1990 Suburban won't start

I'm new to the board, so forgive my ignorance in advance. I'm trying to repair what may be a complicated issue by myself.
I have a 1990 GMC Suburban 2500 7.4L 2W Drive. I was driving to work last week and the car completely cut out. I could not get it restarted.
Since then I have replaced the Fuel pump, fuel filter, fuel pump relay, ignition coil, distributor (the entire distributor including pickup coil and module), plugs, plug cables. I still can't get the truck to start and I'm at my wits end. Any suggestions of what to look for next? Sorry for the long post. Thank you.

What kind of testing did you do before you replaced everything? Were there any trouble codes?

Have a helper crank the engine, while you check for spark at the plugs, anything?

With the engine cranking, do you see the injectors spray pattern? How is the fuel pressure?

I'm in some areas that I have never done work before, so again, forgive my ignorance, but I'm trying.
As far as the Fuel Pump, I simply listened for the fuel pump hum. When I didn't hear it, I figured it was just the pump. The rest of the changes were suggested at the parts store. Unfortunately I don't have a pressure tester and honestly I don't know where to check the pressure.
As for the injectors, I'm not quite sure where to look for a spray pattern, also I'm not sure how to test for spark. Any direction would be great. Thanks.

To test for spark, you pull a plug wire off the plug, You can use a known good plug in the boot. Lay metal part of plug on metal part of engine, have somebody crank engine, watch for spark at tip of plug. You can get a cheap spark tester at the auto-store. I have used a phillips screwdriver in the plug boot, hold shank of screwdriver close to engine ground, crank engine watch for spark jump to ground, probably safer to use a spark tester. You don't have to hold it in your hand.

As far as the injectors, I guess your TBI, you remove the air filter housing, the injectors are in the top of the throttle body, got a couple of wires going to each one. Gas should squirt out the bottom of the injectors, with the engine cranking.

Thank you for info! I'll give it a shot and let you know the results.

Hi. I'm working on the car without a helper, so I'm somewhat at a disadvantage. After several attempts at getting it to turn-over, still nothing. I'm getting spark, however, from the best I can tell, I'm not getting spray out of the injectors. I was thinking of getting a noid lite. Would you recommend that approach? If I'm getting current to the injectors, but no fuel spraying, do you know of a next step. If I'm not getting current, any ideas there? Thanks for the help.

When you say it won't turn-over, that means it won't crank? Does it crank, when you hit the starter?

You really need somebody to crank the engine while you do the testing.

The B+ to the injectors should go hot when you turn the key on. You can unplug the connector from one of the injectors, turn the key on, check for voltage at one of the terminals with a 12 volt test-lite. If there is no voltage, you may have a blown fuse, somewhere.

Yes, if you use a noid lite plugged into the injector plug and crank the engine, the noid lite should flash, meaning, there is B+ and ground at the injector plug.

You should have done your testing before you bought any parts. You can't hardly do any testing without a helper to crank the engine. I don't know how you tested for spark at the plugs without a helper? I guess you could lay the spark tester where you could visibly see it, while you cranked the engine. Are you sure you have spark with the engine cranking?

I reread some of your posts, so the pump won't run? My hearing is no good, I can't sit in the vehicle and hear the pump run. Before the vehicle quit, could you turn the key on and hear the pump prime from inside the vehicle? Just by turning the key on, not cranking, the pump should run for a few seconds.

There should be a fuel pump prime connector, You should be able to trace it from the relay. I believe it is a red wire. You can run B+ to that connector, the pump should run. After you hook it up, you can listen at the rear of the vehicle. Don't have to use the key or anything. If you run B+ to that connector, you have to be sure what your doing, I can't see it from here. If you try that test don't forget to unhook the wire.

Thanks for taking the time to post a response. I have learned my lesson the hard way on this one. Being the only vehicle I have, I was in a rush to try to get it working again and did what I thought was right based on what others were telling me to do.
Yes, I can hear the pump turn on and prime. That I'm certain of. I did place the spark tester where I could see it, but it was getting into the early hours or the morning, so maybe I saw (or thought I saw) what I wanted to see. I'll try it again.
I do know for certain I'm not getting fuel spraying out of the injectors. I had my 2nd grader crank it for me last night while being right on top of the TBI. By the time I got to NAPA last night, they were closed. I'm going to pickup a noid light tonight.
Thanks again!

Tried getting spark again tonight, and no spark. Also can't get a voltage readout on the injector. Any thoughts on next steps?

I can't tell you how to spend your money, as far as parts and testers. It's your money, your decision. All I can do is give you ideas.

I don't know how you checked for voltage at the injectors? If I was looking for voltage and didn't care about the ground side, I would use a 12 volt test-lite. So you see, here we go again, if you don't have a test-lite? I can't tell you to buy all this stuff.

If you use a test-lite, ground the alligator clip to a metal part of the engine, that you think is a good ground. With the plug loose from the injector, touch the pointed end of the test lite to one terminal or the other, with the key on, you don't have to crank it. The lite should come on.

If the computer doesn't see an rpm signal, it won't ground the injectors.

I can't believe you replaced all those parts and didn't know how to check for spark at the plugs. Even if your just killing time, shooting the breeze. Ha, I'm doing the same thing. Every post I make, gives me more credibility on this site. I don't mind talking to you. thanks

Thanks again for your ideas. I'm learning a lot about engine electrical and fuel delivery systems quickly. If I could, I would just take it to a shop. However, with 6 kids to take care of, every dime is important. I don't feel too badly about changing out the parts that I replaced. Even a visual inspection showed the parts were either worn out or wearing out quickly. For instance, the sock at the end of the pump was completely disintegrated.
This is my only vehicle and I can't continue renting a car, racking up more costs.

Yes, I did use a 12V test light. No, I did not get it to light. I'm also positive there is no spark. I took the distributor cap off and the rotor does turn. Even if the timing is off, the chain shouldn't be broken (which a guy at NAPA swears it was a broken timing chain). I greatly appreciate your help. Your ideas are the most credible that I have received. Thank you.

The ignition module on your 90 takes the ac signal from the pickup coil and converts it to a dc signal that the ECM uses to control the fuel injectors and the ignition timing.

I don't have the factory manuals in front of me but you can test if the ignition module is sending the signal to the ECM using a test light. I can't remember which wire it is but it is in the 4 wire connector.

This link shows the ignition module but note that the ECM pins are different on yours http://www.slantsix.org/articles/dibiase_efi/gm-ign-module-schm.jpg

Some parts stores can test the ignition module.

If the ignition module is sending the signal but you still dont have spark, it is probably the ignition coil.

//2000CAYukon

Thank you. I'll check the Ignition Module tonight.

Thank you. I'll check the Ignition Module tonight.

The reference signal sent from the ignition module to the ECM is a purple/white wire.

Pickup coil resistance should be 500-1500 ohms.

//2000CAYukon

Thank You. I get spark going to the ignition coil. However, I can't get a voltage reading going to the 4 wire lead going into the ignition module at the back of the distributor. I have checked with a test light and a voltmeter. Any ideas? Thank you.

Thank You. I get spark going to the ignition coil. However, I can't get a voltage reading going to the 4 wire lead going into the ignition module at the back of the distributor. I have checked with a test light and a voltmeter. Any ideas? Thank you.

You need to touch the test light to the ignition module pin for the purple/white wire. It may be easier to take the ignition module to a parts store to be tested.

You can also put your volt meter on the lowest ac scale and connect it to the pickup coil direct. It should generate 1 or 2 millivolts while the engine is cranking.

//2000CAYukon

I was able to get the right milivolts coming off the pickup coil, but no light on the purple/white wire lead on the module.
I figured it was a bad module, so I took the whole distribuor back and got a new one with a new module. I upgraded the cap to a Borg Warner. Everything back in, still no start and no spark at the plugs. I'm almost ready to give up. Thanks,

I was able to get the right milivolts coming off the pickup coil, but no light on the purple/white wire lead on the module.
I figured it was a bad module, so I took the whole distribuor back and got a new one with a new module. I upgraded the cap to a Borg Warner. Everything back in, still no start and no spark at the plugs. I'm almost ready to give up. Thanks,

Is the coil getting power? I assume you have checked all the fuses including the fuel pump fuse (near the fuel pump relay).

I have the 90 factory service manuals at home. I will take a look later tonight when I get home and see if I can be of any help.

//2000CAYukon

You have been extremely helpful!
No, I did not check the fuel pump fuse. If you can point me in the right direction of where to locate it, that would be great.
Up working on it late again last night and I've had some success. Now I have power to the coil and spark in all the plugs. I'm getting the correct MiliAmp reading off the injectors, but still not getting spray. Not enough fuel pressure? Do the injectors need to be re-built? I appreciate your help!!

You have been extremely helpful!
No, I did not check the fuel pump fuse. If you can point me in the right direction of where to locate it, that would be great.
Up working on it late again last night and I've had some success. Now I have power to the coil and spark in all the plugs. I'm getting the correct MiliAmp reading off the injectors, but still not getting spray. Not enough fuel pressure? Do the injectors need to be re-built? I appreciate your help!!

I have a pickup but the manuals include the suburban. On my truck the fuel pump fuse is under the black cover on the passenger side of the firewall. Not sure if is in the same place or not on yours. There is also a fuel pump test connection that bypasses the relay and fuse so that you can test the pump directly. I forget where it is (never used it) but I know it has one.

Unfortunately, the TBIs don't have a test port in the fuel line so it is hard to test the fuel pressure. You need a tool that replaces the fuel filter so a gauge can be hooked up. Pressure needs to be 9 - 13 PSI. If you have not replaced the filter, that would be a good thing to check (or just replace it).

I won't be home for a couple of hours but I will try to find where the test connection is for the fuel pump. You should be able to hear the pump when you apply 12 volts to the test connection.

//2000CAYukon

The test terminal is part of the ECM connector under the steering wheel. See http://www.troublecodes.net/GM/ and apply fused 12 volts to pin G.

There is an oil pressure switch that can cut off fuel if the oil pressure is too low.

The fuse is under the black cover.

If you have an injector test light, does it flash when you try to start the truck and it is connected to the injector harness?

Good Luck,

//2000CAYukon

Thank you for getting me the info. Finally I was able to get pulse going to the injectors and fuel getting up to the throttle body. However, I'm still not getting spray. I started to take the TBI apart and found most of the seals/gaskets were almost worn away completely. When I put it back together I had leaks everywhere. I'm going to try a TBI rebuild tonight (I had to wait for the tune-up kit) and see if that corrects the problem. Would you suggest also replacing the fuel pressure regulator while I'm in there? Thank you again for all your help! Do you know the specific tool I would need to check the fuel pressue? That is something that I don't have.

Thank you for getting me the info. Finally I was able to get pulse going to the injectors and fuel getting up to the throttle body. However, I'm still not getting spray. I started to take the TBI apart and found most of the seals/gaskets were almost worn away completely. When I put it back together I had leaks everywhere. I'm going to try a TBI rebuild tonight (I had to wait for the tune-up kit) and see if that corrects the problem. Would you suggest also replacing the fuel pressure regulator while I'm in there? Thank you again for all your help! Do you know the specific tool I would need to check the fuel pressue? That is something that I don't have.

I got a rebuild kit from Kragens that had a new regulator in the kit. The regulator is located in the TBI itself.

If you don't already have a fuel pressure tester you can get something like http://www.actron.com/product_detail.php?pid=16175 (but the fuel tester will only work with the adapter that it came with. The threads are different so you need to understand that if you buy this gauge).

If you already have a gauge, then you can get something like http://www.sjdiscounttools.com/ta37650.html

Good luck.

//2000CAYukon

I think I'm going backwards. I finished the TBI re-build and had some difficulty cranking. I figured it was the starter, which I then replaced. Now I can't even get it to turn over all the way (I might get one good turn, then I hear the clicking sound). I know I have all the starter connections on and tight because I took my time. Maybe a bad starter? Kragen usually has ok parts, but I already had to exchange a distibutor that I got from them as well. Any thoughts?

I think I'm going backwards. I finished the TBI re-build and had some difficulty cranking. I figured it was the starter, which I then replaced. Now I can't even get it to turn over all the way (I might get one good turn, then I hear the clicking sound). I know I have all the starter connections on and tight because I took my time. Maybe a bad starter? Kragen usually has ok parts, but I already had to exchange a distibutor that I got from them as well. Any thoughts?

Clicking usually means there is not enough power to turn the engine over. Double check the battery connections. Make sure the battery is fully charged.

Does it click if you try to jump start it?

//2000CAYukon

your head light seems to be ok or when the problem occurs the interior main ligh turn off?

Yes. Headlights and Interior lights are fine. The battery has a full charge (I just replaced it as well) and I tested it to make sure it was throwing the right voltage.
Still not getting it to turnover. It sounds like it wants to go and I'll get a few good turns out of the belt, then it will stop.
Someone mentioned it may be head gaskets and not enough compression. Any thoughts. Thanks again!

Yes. Headlights and Interior lights are fine. The battery has a full charge (I just replaced it as well) and I tested it to make sure it was throwing the right voltage.
Still not getting it to turnover. It sounds like it wants to go and I'll get a few good turns out of the belt, then it will stop.
Someone mentioned it may be head gaskets and not enough compression. Any thoughts. Thanks again!

To me turnover means the engine is not moving at all when you turn the key on. So does the engine move at all when you turn the key?

The timing chain may have jumped a tooth (or two). I replaced mine last year (115K on my 90 GMC K1500 Sierra) and it was pretty loose.

By all means, a compression check would be a good thing to do at this point.

//2000CAYukon

I get about one full rotation out of the Serpentine belt. Then the clicking sound even with jumper cables on it. Thats about all I can get. If I turn the distributor I might get 2 or 3 rotations out of the Serpentine belt, and then back to clicking. Sorry I was unclear about turnover.

I just read so much here that 2 things just happened.1,I have a headache now,2 I completely forgot all that you have done,what your problem is or was or still is with new ones.If I recall you have a big block,sounds like you crancked the crap out of your starter,that's alot of engine to cranking as much as you have done.Could you please put up a short list of : Issues now,before starter explosion.The starter issue was caused by not getting it to go and winding the crap out of it so it don't count as an issue,it is actually a result.I love the older chev stuff and will help you as will the rest of us,just slow down dude.I get the impresion your going 300 mph.

Sorry for the long thread. I have had some expereince doing suspension work (ball joints, control arms etc.), but am learning the engine electical/mechanical and fuel delivery parts. Here is a quick summary. Driving to work the old Suburban's engine cut out. I didn't hear any noises, it just shut down. I could not get it restarted. Here is what happened since then.

#1. Couldn't hear the fuel pump, so I dropped the tank and replaced it
#2. Replaced the fuel filter
#3. Replaced the fuel pump relay
I still could not get it to start at that point and upon recommendation I started replacing other ignition components.

#4. Replaced the distributor (new w/ pickup coil and module), rotor and cap
#5. Replaced the ignition coil
#6. Replaced the spark plugs and plug wires. (I'm getting spark)

Still, a no start situation...resulted in a trashed starter.

#7. Replaced starter and battery

On recommendation...

#8. Rebuilt the TBI. (I'm getting pulse to the injectors)

Before I was getting the engine to turn, but not turn over. Now I'm getting maybe one or two good turns (watching the serpentine belt), then it stops and starts clicking.

I have been trying to get this done as this is my only car. Renting has become way too expensive.

Sorry for the long post.

Clicking usually means that the starter is not getting enough power to start the engine. Inspect both ends of both battery cables. Make sure connections are clean and snug.

You may want to do a compression check to make sure that the compression is good. Too high or too low will make it hard to start.

//2000CAYukon

First things first,just because you bought a NEW part don't mean it's any good.Listen,read I guess lol, pull the plugs,disconnect the power to the coil ( this will be very important soon), now try to roll the engine over.If your getting it to roll now then one of 2 things,it;s full of fuel in the cyls or the chain jumped.If it is full it soon come flying out of plug holes.Did you have the dist out of the truck?If so maybe your out of time.Pull #1 plug,stick finger over hole,have a partner ( cheat code= tap into the the little stud or purple wire down at the stater and that will roll the engine when you touch it to the batt +, just like you turned the key) just bump the starter enough to roll the engine at small intervals.When you get to compression out the hole you are close to Top Dead Centre.Line up the timing marks on the crank pulley and then make sure rotor is at #1 spot on the cap.Recap= Check for severe flooded,check for compression,check for TDC timing at cap.Pull the oil dipstick to make it does not smell like gas, if it does don't try to start it,I have seen the oil pans blow up when they fire.Let us know and we will go on from here.

With the plugs pulled and the power disconnected to the coil, I'm getting it to roll fine. I don't see anything shooting out of the plug holes.

Still no success. I hooked everything back up, used jumper cables and got it to turn but not start. No fuel coming out of the plug holes, and I made sure I was TDC. Not sure what to try next or what the diagnosis might be. Thanks for the help.

I also put a little gas in the TBI to see if I could get it kick started. Still nothing. I heard a few pops, but that was it. Still turns, just not firing.

If your positive that the dist is firing at the spot then you must have the firing order out.We have to get you back on track here.

Still no success. I hooked everything back up, used jumper cables and got it to turn but not start. No fuel coming out of the plug holes, and I made sure I was TDC. Not sure what to try next or what the diagnosis might be. Thanks for the help.

Are you sure you were TDC on compression stroke? With your finger over the #1 spark plug hole, make sure you feel compression (finger should feel pressure) and then rotate to TDC.

I have seen the balancer go bad and rotate leaving the timing marks incorrect. Does the rubber look good between the two pieces of the balancer?

Also, if you have it at TDC compression stroke, pull the drivers side valve cover and look at both valves on the #1 cylinder. They should both be closed. If the timing chain jumped, one may be open.

Good luck,
//2000CAYukon

I've been trying to get the engine to fire up for the last 3 days. I re-did the firing order, pulled the valve cover (everything looks fine). I got it to fire up for about 5 seconds, then it died. I can get short spurts of turn-over, but can't keep it going. Also, every once and a while, I'm getting poping sounds out of the TBI. Anything else I should check? Thanks you! Happy Holidays!!

I was down and out for a few days,just wondering how you've made out?

Thanks for checking in. Still in a no start situation. I'm getting "popping sounds" coming out of the Throttle Body, but can't get it to turn over. I've checked and double checked the firing order. Not sure what to try next. I'm about ready to give up.

Working on the truck again this afternoon. I've got it to the point where I have the engine turning over for a few seconds. It sounds like it wants start, but doesn't keep going. Do you think timing is still off? Thanks for your help.

Working on the truck again this afternoon. I've got it to the point where I have the engine turning over for a few seconds. It sounds like it wants start, but doesn't keep going. Do you think timing is still off? Thanks for your help.

This sounds more like the timing chain has jumped. This happened to me when I was 16. The cam gear in those days was nylon coated for noise reduction. The chain jumped a tooth and it was real hard to start and had very little power.

Did you evey perform a compression test to see what it was at? Has the chain ever been replaced? I replaced mine a year ago Thanksgiving (90 GMC K1500 Truck) and was very surprized at how loose the chain was.

//2000CAYukon

Thank you for the advice. No, the timing chain has never been replaced. Most of the parts I've been replacing were probably on the car when it rolled off the production line in 1990. I'm going to replace the chain. While I'm there, is there anything else I should look for/replace? Thanks again.

Thank you for the advice. No, the timing chain has never been replaced. Most of the parts I've been replacing were probably on the car when it rolled off the production line in 1990. I'm going to replace the chain. While I'm there, is there anything else I should look for/replace? Thanks again.

You need to lower the oil pan in front or you will end up needing a new pan gasket (ask me how I know :grinyes: )

Before you jump in to this, I need to ask if you have done a compression test and what were the numbers.

If you do the chain, make sure you rotate the crank to TDC so you can tell if the chain was off or not.

Good Luck!

//2000CAYukon

Sorry for the delay. I just got the compression tester last night. I'll run the test tonight and post the numbers for your advice.
Thanks again for your help.

Here are the results from the test. Readings (psi): Cyl. 1 = 165; Cyl 2 = 180 Cyl. 3 = 170; Cyl. 4 = 175; Cyl 5 = 155; Cyl 6 = 140; Cyl 7 = 140;
Cyl. 8 = 155.
I found one of the only timing chain sets in the city (without having to special order it). I'm thinking that I might as well do that job this weekend. I've never accomplished this task. Can you tell me how to make sure I'm TDC?
Thank you for your help.

I forgot to mention, it usually attained the reading at 5 compression strokes. The readings went up around 60 psi per stroke.

Can you tell me how to make sure I'm TDC?
Thank you for your help.

The timing mark on the balancer lined up with the 0 on the timing marks is either TDC for #1 or #6. If you remove the #1 plug and put your finger over the hole, you should feel pressure as you get near TDC for #1.

You will be a balancer remover/installer to do this job. This tool can usually be rented.

When I replaced my timing chain, I removed the timing cover, then lined up the timing marks (I used the bolt for the balancer to rotate the engine). Removed the old chain and installed the new chain and gears.

Is there anyone who can give you a hand if you need any help?

//2000CAYukon

I forgot to mention, it usually attained the reading at 5 compression strokes. The readings went up around 60 psi per stroke.

That is the correct way to do it; although, I would have done at least 2 tests per cylinder.

Best of luck,

//2000CAYukon

How many miles on your engine? Make sure that your plug wires are on the right order 1-8-4-3-6-5-7-2 recheck. As you stand at the front of the suburban looking at the engine 1-3-5-7 on right drivers side, 2-4-6-8 on left side. Even after 30 years I have switched wires accidentally and get popping noises from carb or TBI.

I did two checks per cyl. to ensure accuracy.

Unfortunately, it will probalby just be me. I really don't have anyone to help out. I've got everything apart but the timing cover. I have to get the harmonic balance puller today. If there is anything else you can think of, let me know. Thanks again.

I did two checks per cyl. to ensure accuracy.

Unfortunately, it will probalby just be me. I really don't have anyone to help out. I've got everything apart but the timing cover. I have to get the harmonic balance puller today. If there is anything else you can think of, let me know. Thanks again.

The only thing that I can think of might be a gear puller for the crank gear. In my case, it came off without it. You won't know until you get the cover off.

Make sure you loosen all of the pan bolts so that the timing cover comes off with out damaging the pan gasket.

Before you remove the chain, you should try to align it so you can see if the marks are off. You can do this by rotating the engine by hand.

//2000CAYukon

Thank you. I got a gear puller when I picked up the harmonic balancer remover tool. The tool came without instructions, so I'm not quite sure how to remove the balancer. Do you have any words of advice. I was reading a few posts and it seems like it could be a difficult job. Thanks again.

Thank you. I got a gear puller when I picked up the harmonic balancer remover tool. The tool came without instructions, so I'm not quite sure how to remove the balancer. Do you have any words of advice. I was reading a few posts and it seems like it could be a difficult job. Thanks again.

Does this help? http://www.diynetwork.com/diy/en_engine_block/article/0,2021,DIY_13807_2276768,00.html

Are the marks lined up or does it look like it jumped a tooth? Is the chain pretty loose?

//2000CAYukon

I haven't opened the timing cover yet, but I would suspect the chain is quite loose. Last night I was trying to take off the front piece to the Harmonic Balancer. When I crank it, the whole engine turns. There are 3 bolts, one in the middle, one top and one bottom. How does that piece come off? I gave up after I got frustrated about 1:00 a.m. Thanks,

There are 4 bolts holding on the pulley to the harmonic balancer usually. 3 are 9/16 and in the middle a 5/8 .

There are 4 bolts holding on the pulley to the harmonic balancer usually. 3 are 9/16 and in the middle a 5/8 .

The middle one can also be tough to break loose (I forget the torque setting but it is around 140 lb-ft). An air wrench comes in real handy here. Assuming that you dont have one, use a breaker bar or large screwdriver to stop the balancer from moving (be sure that it rests on the block) and break that sucker loose.

//2000CAYukon

Oh man,now we got into the chain.I do not think that it is an issue at this point.You more than enough squeze.Once again I was out for a bit and was not on top of this thread.It really sounds like the dist is out to me.Yes the chain may be tired but I don't think it jumped.I just have never seen a engine throw out a 145-160 comp squeze and the chain be bad.24 years on me man,never seen that one.I'll bet dollars to doughnuts that when you had that bad boy "popping" thought the tbi if you just moved the dist it would have fired.I wish that I was able to whip in your driveway and help you out dude,to me this is just getting(passed) painful for you.

Help. I've been trying to pull off the balancer for the last two days. Is there a trick to getting it off? I pulled one of the washers out of the center of the balancer, but there may be something else I'm missing. The screws I'm using keep pulling out of the balancer.I know I have the right size bolts going through the yoke. Also, the rubber has almost completely "walked" in between the balancer. There is only about 1/4 of it in the right spot. Any suggestions?