No Start/Fuel Pump Diagnosis

Hey guys whats up. I just replaced a fuel pump on my brothers 96 Blazer 4.3 SCFI. I'm not sure what brand the fuel pump is yet I might be able to find out but I know its not an AC Delco. The fuel pump comes with it's own connector and according the the instructions I followed them to the letter. 4 wires 1 prp, 1 grey and 2 blk and one of the black wires have a white stripe.

Ok so I installed the fuel pump I have one side held up by the fuel petcock and the other side held up by two 4x4 blocks of wood it's in a bit of a decline it's not even or leveled I should say, however the pump is wired. So I figured I would try to start the blazer and make sure it would work before I put the tank up completely. I used my car to jump the battery so it wouldn't drain from cranking plus I'd say the battery had a little bit more than half of its juice.

Summary: I turned the key on for 2 minutes so the pump can pressurize the fuel lines then I went at it and it just wouldn't start. I noticed the fuel gauge wasn't working ever since I installed the fuel pump so I'm assuming that the wiring is wrong what kills me though is I did exactly what the instructions told me. I'm also going to check the crimp connections. Basically I'm looking for some ideas something I might not have thought of yet because I want to get this car done ASAP.

Note: Car has been checked for spark.
Fuel shraeder valve seems not be pressurized.
and the car starts up with starter fluid.

Thank You

Did you use the heat shrink connectors that come with the harness pigtail?
Does the pump buzZ when the key is turned on?
Check what brand the pump is. Some of those Chinese pumps are total garbage right out of the box. Sometimes I have had to get 3 pumps before getting one that worked.

There were no heat shrink connectors just the regular darker red/blue colored nylon butt connectors. The instructions do say to use heat shrink tubing but they did not come with the package which it clearly shows in the picture upon purchasing.

Pump definitely buzzes when key is turned on and all I can tell about the pump is that it is sold on ebay from AM-Autoparts the seller. Thanks for the reply


http://www.ebay.com/itm/96-Blazer-Bravada-S-15-S10-Gas-Fuel-Pump-Module-with-Sending-Unit-NEW-/110920227791?pt=Motors_Car_Truck_Parts_Accessories&hash=item19d35c5bcf&vxp=mtr

Even though you got detailed instructions. I have seen some after market pumps where the + and - was reversed from the original pump.

Really? that's bad...

I don't believe that is the case for my situation because I can hear the fuel pump prime when I turn the key on. Also I want to correct a previous statement. The fuel line did have fuel coming out of it when I checked today, and I think yesterday when I checked for pressure I didn't have the key to the on position.

I just double checked the wiring and terminal A of the connector is purple, B is grey, C is solid black, and D is Black with white stripe. I jumped the fuel pump to check for voltage just to see if there was a decent amount and the pump wire had 11.7 volts and the purple wire had 7.6 but I did it twice and I could tell the battery is dying because it dropped 3-4 volts on each wire the second time I'm also going to charge the battery because I read that these blazers need to crank pretty fast to start up.

When you initially turn the ignition to the RUN position, the grey wire at the fuel pump module must show battery voltage for ~2 seconds, then drop to zero volts. Both black wires must show less than 5 ohms resistance to ground at all times. Check it out and post your results.

Thank you for the response Old Master, when you say the fuel pump module do I have to check right at the connector? or can I check at the splice with the wires connected? because when I checked the voltage on the grey wire it wasn't connected and it was constant voltage. Thanks Boss

edit: I was thinking isn't it safe to assume that the fuel pump module shuts off after 2 seconds because when I turn the key I can hear the fuel pump prime for 2 seconds, what do you think?

Best to check voltage and resistance right at the fuel pump module connector. That way you know that power and ground are being supplied the module. Ideally you should check it right at the pump motor, which would test all wiring and connectors.

When you initially turn the ignition to the RUN position, the PCM activates the fuel pump relay for ~2 seconds. During that time, (pump prime) if the PCM does not receive data from the crankshaft position sensor, (which it won't because the starter is not turning the crankshaft) it deactivates the fuel pump relay. When the ignition is in the START position, the fuel pump relay is activated continuously.

Probably ought to check fuel pressure and leakdown at the service port. Key ON, engine OFF, fuel pump running: pressure must be 60psi to 66psi and must remain above 55psi for at least 10 minutes after the pump shuts off.

This fuel delivery system, (CSFI) must have correct fuel pressure to start & run properly. Aftermarket pumps don't make the grade. Fuel pumps are no different than anything else, you get what you pay for. If you want a pump that will work properly, and last, you need an AC Delco or Delphi pump. They are typically in the $180 range.

Ok that sounds like a plan. I did see a AC Delco sending unit module for $90 on ebay but it wasn't the whole assembly if I had seen it before I would have grabbed it.

Get it diagnosed first, then make a decision.

I will I'm going to stay with what I have but if I would have saw that AC Delco first I would have bought it before the one I got. The pump is definitely pumping fuel I just have to see if it's pumping enough to get to 55-61 PSI. So that means I need to purchase a fuel pressure tester, maybe a harbor freight one.

So that means I need to purchase a fuel pressure tester, maybe a harbor freight one.I bought one from Harbor Freight and it is o.k. I think I paid $15 - $20 for it. However, I wouldn't swear to its accuracy. I would certainly try one. Keep your receipt and if you find that the gauge is inaccurate, take it back and get a refund.

I just have to see if it's pumping enough to get to 55-61 PSI...

1996, (CSFI) fuel pressure spec is 60psi to 66psi, (key on, engine off, fuel pump running). If it's less than 60psi, you will have problems.

I swear to God I saw 55-61PSI yesterday on my alldata now it says 60-66psi oh well anyways I checked for voltage and it it read 11.45 volts while the pump was priming and it then stopped after 2 seconds. I also checked for resistance it was reading from 0.03 to 0.04 ohms at the connector on the grey wire. It was definitely pumping fuel as well so I'm headed to go get a fuel pressure tester.

On 1995 and older CMFI systems, fuel pressure spec is 55psi to 61psi. If pressure is too high or too low on either system, it will cause problems. If you want to be sure you have correct information, you need the (manufacturers) factory shop manual. All Data is a much better choice than Chilton or Haynes, but aparently they make mistakes too.

Make sure the black ground wires show less than 5 ohms to ground at all times.

Well i just grabbed a fuel pressure tester kit from Harbor Freight not sure if I'm going to do it today since it's getting dark. As far as the psi on AllData I could have selected the wrong year like 95 model and came up with that figure.

Ok.....so today was a busy day for me however I did attempt to check the fuel pressure. Now the fuel Pressure test kit I bought at HF is this one: http://www.harborfreight.com/automotive-motorcycle/diagnostics/fuel-injection-pump-tester-92699.html unfortunately it started to leak on me and then fuel got into the gauge. It did not leak at the fuel test port valve but at the top with teflon tape or pipe threading compound.

Even though the kit malfunctioned I did get to get some type of reading. The first turn of the key the system wasn't pressurized so it ended up around 30ish the second time it was within spec between 60-66psi and it did hold steady within 56-60psi but that is when the leak showed up and it slowly started to decrease in pressure so I'm going to try to repair the guage and give it another shot to see what happens.

Note there is another thing that I didn't mention. I noticed the fuel in the tank was pretty dirty like brownish. The fuel is fairly new less than 3 weeks old.

Take it back and try another one. You know there's a problem with the gauge, so you can't trust it to be accurate.

This is a pretty decent tester and most auto parts stores have them:
http://www.amazon.com/Actron-CP7818-Fuel-Pressure-Tester/dp/B0006V2BI2/ref=sr_1_2?ie=UTF8&qid=1353378056&sr=8-2&keywords=actron+fuel

Well I took the rubber round protector off this time I used a lot of teflon tape and used two wrenches to tighten up the tester. I had to really tighten it this time and it worked not 1 drop of fuel dripped from the connections. I also made it easier by removing a few things so it could have it's own resting space.

Anyway I did some readings. The results were good when the pump was priming for 2 seconds every time, it was like 64psi, but when I turned the key off or if I left it on it would hold between 55-58psi for 20 seconds maybe 30 or so and then it would slowly leak down. Another thing to note is the psi would drop quickly to 10 psi this happened only twice but when I tried to create that symptom again I couldn't do it.

I'd rather grab one at sears for 32.00 then wait for the shipping I need this car out of my front house thanks for the link though I will notify my brother about that tester anways.

edit: I was thinking about my situation and if I had a bad pressure regulator the blazer would run bad or stall sometimes but with the readings I'm getting that is enough to start the car.

Agreed, regulated pressure is OK BUT, the leakdown is a problem. Next step is determine what's leaking. Could be an injector, a poppet valve, the regulator, a line inside the plenum, fuel pump check valve, the line from the pump to the module etc. The fuel pressure tester needs to be modified so it connects directly to the fuel filter. All fuel pressure and flow must end at the tester, (no fuel can be allowed to reach the plenum). Key ON, (engine obviously off), fuel pump running, pressure must be 73psi to 108psi and must remain above 55psi for at least 10 minutes. The results from these 2 tests will determine if the leak is in the tank, or in the plenum.

Mr. Old Master I seem to have ran into another bump on the road to getting this POC vehicle to a starting state. I went to go pinch the flex part of the fuel line and read the fuel line pressure which is after the fuel filter and my fuel pressure tester died so I'm getting it replaced tomorrow. I couldn't modify the tester to fit onto the fuel line I just didn't have a big enough fitting for it so tomorrow when I get a new one I'm going to check the intake side of the fuel supply line and see if there is a leak.

Pretty simple to make an adapter that will connect to the fuel pressure tester. Disconnect the quick connect fitting from the fuel filter. This fitting will connect to the filter: http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_steel-body-fuel-line-connector-3-8-inch-dorman--oe-solutions_9110024-p?searchTerm=fuel+line+connector From that fitting use a piece of 3/8" fuel injection rated rubber line and put one of these in the other end of the hose: http://www.tuxedoparkbrewers.com/index.php?main_page=product_info&cPath=7_60&products_id=775 Then attach your fuel pressure tester to the 1/4" flare fitting.

I'm a little confused, my fuel filter doesn't have any quick connects. I don't see how that Dorman universal connector would work or connect since the fuel filter is a threaded female.

In that case, substitute the quick connect fitting in the previous post with this one:
http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_steel-fuel-line-repair-kit-3-8-inch-x-4-inch-with-16mm-fitting-dorman--oe-solutions_16140334-p?searchTerm=fuel+line+repair

It already has the barb, install the rubber line and the adapter and you're good to go ;)

That'll work.

I got the new fuel pump tester kit I had someone who works close by HF bring it back for me. When I opened the new box I could tell it has been used there was two tiny little scratches on the glass and the insert part of the gauge had green oxidation on it. I still gave it a try and when I turned the key the needle didn't move I tried 2 more times and then finally it jumped up to 10psi so I kept cycling the ignition to increase the psi because that was the only way I could get the psi to go up. I got it to 54psi and it wouldn't go further. I paid attention to the leak down and it wasn't holding either. I can't go by the readings off this tester so I'm going to get another one since it's been paid for and possibly a different brand kit as well. The one good thing was that the gauge didn't leak at the connections this time, you really have to put a decent amount of tape it's not like air tools.

Well today I finally got to test the fuel pressure right and for the FP prime I got 61 almost 62psi and when the prime would stop the needle would jump to 54psi and it would slowly leak down a number every 10-20 seconds. I still think I have enough psi to start the car but there is definitely a leak somewhere. Tomorrow I will isolate the leak. I'm starting to think this might have something to do with the injectors, I don't see anything else stopping the car from starting up.

Leakdown is excessive, 10 minutes after the pump shuts off, the pressure must be 55psi or more. Check the fuel pressure and leakdown at the fuel filter and post your results. If leakdown is excessive in the tank, the cause must be repaired in order to diagnose any other leaks.

Ok I finaly got around to checking the pressure at the fuel filter. I have pictures of the adapter. So with the key to the on position and engine off the PSI reading went to 100PSI and a little bit over. It held at 100PSI for a few minutes within 10 minutes I'd say the PSi stayed over 95PSI and in 20 minutes it stayed at 90PSI. I bought these fuel pinch clips http://www.google.com/url?source=imglanding&ct=img&q=http://www.autohausaz.com/secure/PartImages/22850LISLE.jpg&sa=X&ei=thi8ULjTOaXv0QGTtIHAAw&ved=0CAkQ8wc4_QE&usg=AFQjCNEoyANUmV3ESGpoEpay8csg_HaKCw

Tomorrow I'm going to check the other side of the fuel line from the fuel filter to the spider and regulator and see what happens I think I have a problem in the intake area.

Nice job with the adapter!

The fuel pump is fine. The leakdown is in the plenum. Pull it off and have a look around. After the plenum is removed, you can reinstall the fuel lines to the metering block, activate the pump and look for leaks, possibly the regulator. If you can't see any leaks, either an injector is leaking or the regulator is leaking internally. Either case, might as well do the injector upgrade, it comes with all new injectors and the regulator. Post your results.

Thanks but you deserve the credit it was your idea. Ok sounds like a plan I'm going to do some disassembling I hope I find some results. Thanks again

Maybe my idea, but you built it! I've never made one like that, I built this one:
http://i561.photobucket.com/albums/ss58/cwhook/DSC_0008.jpg

The shut off valve allows me to check maximum pump output pressure, pump leakdown, regulated fuel pressure, plenum leakdown or allow the engine to run. It installs inline at the fuel filter so it's quick and easy. Quite a bit more expensive, but it tests more stuff. Only thing it doesn't pinpoint is internal leaks with the regulator & injectors, but, it does tell me if the leak is in the plenum. For leaky injectors I use the injector balance test on the scan tool. A similar fuel line shut off tool will identify an internal leak in the fuel pressure regulator.

Man that's a nice setup do you have 2 testers or you just never use the fuel port? anyhow I might buy another one just to have a inline tester and swap out the adapters for each specific car.

Micscience

I've got a couple of testers along with stuff I've made. Too expensive to buy 'em from Snap on. That one connects inline at the filter, and I use the regular one on the service port simutaneously. Pressurize the system, shut the valve, and monitor leakdown in the tank and in the plenum at the same time. I made another one that connects inline in the return line, that one can pinpoint an internal leak in the regulator. All you need to do is isolate individual components to determine where the leak is before you start taking stuff apart.... needlessly. It eliminates the guesswork and saves money ;) It's not rocket science, mic ;)

Well I got some progress done but it's like two steps forward then one step back for me it seems. I took the plenum off and had the car started and the fuel injectors were shooting fuel. It looks like there is a leak somewhere can that stop it from firing? I didn't notice the regulator leaking but it was dark and I'm going to check out the regulator more tomorrow. Here are some pics of what I was looking at and a video of the injectors working. The bad news is I really didn't have anyone to crank the engine for me my girl was sick so I grew impatient and had my 3 year old daughter help me lol. This was a mistake because the end result was the intake runner port sucked in two blue paper towel rags I'm almost sure this happened so now I have to remove the whole intake. Oh well....http://www.youtube.com/watch?v=PI0BG-TCHk4&feature=youtu.be

Grrrr, oh well, make the best of it and install a Felpro MS98002T gasket set. Waaaay better than the OEM gasket. If you really want a treat, do the injector upgrade, (Look on Amazon & Ebay) Delphi # FJ10565. When you have the lower intake off, maybe run a drill bit in the holes to clean them out. I've used a powerwasher with good results too. The inside of the plenum is actually quite clean. The black crud is from the EGR system. When the EGR valve opens, it fills the entire plenum with exhaust. It enters the plenum through the small tube in the front of the lower intake manifold. Looks like you've been using good fuel, don't change ;)

You don't have to start the engine to check the regulator, just activate the pump.

Well with the pump activated it didn't leak anything I know when the car is running sometimes it take a few minutes for the regulator to start leaking but the car don't run. I have seen a mechanic blow air indirectly to the regulator and fuel started to appear that way.

Is there anyway I can reuse the gaskets? it's my brothers truck and I know him he is not going to like this. I'm going to try to fish it out some how before I take the manifold off.

edit: also I still don't see why the truck won't start the injectors are squirting and there is spark. Have you heard of anyone blowing air threw the injectors to see if there plugged up?

The two injectors in the video are squirting fuel, with what appears to be a decent pattern, did you check all of them?

Very possible for the regulator only to leak after it warms up.... diaphragm gets limbered up. Blowing compressed air in it? Maybe not such a good idea though. A new regulator comes with the new injector assembly... seems like they're like $80 alone. Professional injector cleaning machine is all that I would recommend for cleaning the injectors. If it doesn't work, or an injector needs to be replaced, it would be cheaper to put the whole injector assembly on it and be done. No, do not reuse the gaskets. Have you replaced the cap & rotor with AC Delco parts?

No I haven't replaced the cap and rotor it looks like it is fairly burned up but I'm assuming that is normal from all the current that goes threw it. I can post a pic of it. I was also thinking maybe the camshaft sensor. I know the cam sensor has something to do with timing in relation to the crank sensor and if the timing is wrong it won't fire up and the starting fluid starts the car because it gets atomized in the intake its already mixed in with the air and gets sucked up into the cylinder but.... that doesn't explain the leak.


here is the break down.

no start
fuel psi good
fuel psi leak
starts up with starting fluid

I want to replace the regulator but I ask myself can it really stop the truck from starting?

Well I got some good news I got the paper towels out there was 4 of them used the vac and blow gun inside the injector port and pics of my cap & rotor.

You lucky dog! I had visions of removing the cylinder head ;)

The camshaft position sensor will not cause a no-start condition. You can unplug it and the engine will still start and run. AND, it would set a DTC if there was a problem with it.


The cap & rotor look pretty nasty.... and they're not AC Delco ;) The white crusty stuff on the terminals is normal. When you install a new cap, always put a dab of silicone dielectric grease on each terminal, inside and out. When the engine is running, voltage jumping from the rotor segment to the cap terminals crystalizes the grease. Stick a new AC Delco cap & rotor on it. Don't waste your time and money on aftermarket. Post the results.

Edit: there's also some evidence of crossfire going on in the cap. Also, the center terminal in the rotor is GONE! Might have to check/adjust camshaft retard also.

The camshaft position sensor will not cause a no-start condition. You can unplug it and the engine will still start and run. AND, it would set a DTC if there was a problem with it.


Well I thought the camshaft had a lot to do with the timing for firing the spark and fuel.

I tested the fuel regulator. I had the pump running for 5 minutes and there was no leak externally not sure if it has to leak gas for it to be bad.

I have the new cap and rotor but I don't know if I should put everything back just to see if that was the problem. Can I try to start the car with the plenum off? I ask because I wanted to clean all the mating surfaces and the top of the lower intake manifold and I don't want to install everything and then have to uninstall it again.

Well I thought the camshaft had a lot to do with the timing for firing the spark and fuel.
Camshaft position sensor, no. Actually it has nothing to do with timing. The PCM uses the data for detecting cylinder misfire and identifying which cylinder(s) are misfiring. If camshaft retard is adjusted correctly, you can unplug the camshaft position sensor and the engine will run perfectly normal. A DTC would be set and the SES light would come on, but it would run fine.



I tested the fuel regulator. I had the pump running for 5 minutes and there was no leak externally not sure if it has to leak gas for it to be bad.
It can leak fuel internally past the valve plate, or externally.
http://i561.photobucket.com/albums/ss58/cwhook/Fuelpressureregulator.jpg

I have the new cap and rotor but I don't know if I should put everything back just to see if that was the problem.
Might as well ;)



Can I try to start the car with the plenum off?
Not a good idea, it might suck something in, like a rag or something ;)

I'm still waiting for the rain to stop here in MA.....

Well I got the plenum back on and I checked my connections to see if everything was good. I went to start the car and it started to turn for a split second and then the engine would come to a halt and I tried 2-3 more times and it did the same thing again. Then all I got was a rapid clicking sound so I went to check the starter and I tapped it a few times I had nobody with me to try and start it up while hitting the starter so now I have to deal with the starter before I can find out what happens.

Like I said 1 step forward and 2 steps back.... This blazer has been sitting for two years so it's like rotting or something.

Sounds like a dead battery or dirty connections. Take the cables off the battery and shine them up, then tighten them up. Charge the battery, and see what happens.

Well the battery is reading at 12.65 volts and the battery is a week old so it is brand new and the connections, at least from the head of the bolt side seems fine however, I'm not sure about the threaded part of the bolt where it goes threw the rubber I'll check that out. Plus I had another vehicle jumping the blazer with the new battery to see if that was the problem and it didn't change after sitting with jumper cables for 15 minutes.

Tomorrow I'm going to check the starter's connections all the way to the battery and the wire. If all seems fine I'm going to have it tested at Auto Zone and if it's bad I'll change it.

After you remove the terminal bolts, pull the rubber boots off and check the actual terminals on the cables. Also check the ground connection at the block, and the positive cable at the starter.

Ok well before I got to do all that I reinstalled the battery one more time to check the symptom again and whata ya know she fires right up!!!

She keeps firing up and running the starter seems to be working for now but I am still going to clean everything up. However I am getting a missfire I checked the DTC and it says it's a P0306 code cylinder 6 missfire.

I pulled the plug to see if it was cracked or corroded it really didn't look that bad. I checked for spark on cylinder 6 wire following the distributor and it seems to spark fine. The only thing I can think of right now is go and change the plugs.

Swap #6 plug with a plug from a different cylinder. Fire it up and see if the P0306 changes to the cylinder you swapped plugs with. That will tell you if the plug is bad.

sweet! thanks man that's a good idea.

If it spits out P0306 after you swap 'em, try swapping a plug wire. If it still spits P0306, might be an injector. The PCM is a great piece of test equipment!

Well I just put new plugs and new wires on the Blazer and it's still misfiring. I can physically feel the hesitation/misfire. So either no fuel, air or spark or it can't compress. I was thinking maybe I missed one of those blue paper towels in the intake. I guess I have to check the fuel injector on cylinder 6. I checked the fuel injectors before when the plenum was off and they were fine I'm sure it's still fine but I will check again. I feel like doing a compression test on cylinder 6 as well. If I get no clues on the misfire by then I'm going to take the intake off.

One more thing the blazer will run smooth sometimes with no misfire for like a minute then it happens. I also have a vacuum leak it seems to be at the reservoir canister the vacuum line is a little to big for the canister connection however I don't see a vacuum leak there causing a misfire just on cylinder 6.

Is P0306 still rearing its ugly head, or has it moved to another cylinder? Have we talked about incorrect camshaft retard being a possibility?

Yes it is showing it ugly head only on cylinder 6. We have not talked about camshaft retard as a possibility but it seems to me that would effect all the cylinders.

One more thing the blazer will run smooth sometimes with no misfire for like a minute then it happens. I also have a vacuum leak it seems to be at the reservoir canister the vacuum line is a little to big for the canister connection however I don't see a vacuum leak there causing a misfire just on cylinder 6.

PS not sure if I mentioned this but it is a (flashing) P0306 DTC.

A flashing SES light means it's a misfire that can damage the converter.

yeah, you're right, (what was i thinking?) camshaft retard would affect all cyls... just like a vacuum leak at the reservoir ;)

If it runs smooth, even for a minute, I doubt it's anything mechanical, or it would run rough all the time. If a chunk of carbon broke loose and lodged in a valve, (holding it open) chances are pretty slim it would always be cyl #6 ;) When does it act up: Idle, cruising speed, light accel, or hard accel? Have you checked the pins in the metering block connector for the injectors?? Maybe a poor crimp, bent pin, etc making a poor connection to #6 injector.

It acts up on any load on the engine and I was wrong before it misfires all the time. I haven't had the Blazer running for longer than 5 minutes since I got it running again. I'll check the pins as soon as I can. I think the catalytic converter is bad but not sure if that would cause the misfire on just cylinder 6. Tomorrow I'm taking off the plenum again and I'm going to inspect fuel injector 6. If it's the same port that I thought there could be a stuck towel inside of I have no choice but to remove the intake just wondering if it's possible to view the valves some how and see if there is a towel stuck some where.

A restricted catalytic converter will affect all cylinders equally.

If it misfires all the time then yes, a stuck towel could cause the problem ;) If I remember correctly, the air inlet for #6 intake runner is the last one on the driver side. Without removing the heads, the only way to see the valves is to remove the lower intake manifold. A fuel leakdown test will tell if an injector is leaking. An injector balance, (contribution) test will tell if an injector is malfunctioning but, everything else mechanical and electrical must be good.

If you remove the lower intake manifold, use a Felpro MS98002T gasket set.

If I remember correctly, the air inlet for #6 intake runner is the last one on the driver side.

Chuck is that the last runner near the firewall? if so than that is two pieces to the puzzle revealed already. The last intake runner on driver side near firewall is the suspect runner that I was unable to remove the shop towel from. Furthermore I removed all spark plugs on the even number side 2-4-6 cylinders one at a time and cranked the engine and listened to the compression sound. Cylinders 4 and 6 sounded the same, as cylinder 6 sounded louder and different its hard to explain the sound but it sounded like something could be muffling the air when is passes threw.

Thanks for the heads up on the gasket and manifold I hope the gasket isn't to pricey. By the way I unplugged the injectors and the ignition when I did that test so Blazer is ok.