Stalled out

[paxfam1]

Okay recently,

Driveing my 98 blazer down the road and it chugs litely, no big deal I keep going.

Next day it chugs a bit more while on the interstate. At this point im starting to wounder, fuel Pump going out?

Next day at every stop the blazer wont idel I come to a stop sign and it just kills. But it starts right back up. Seems to stay running if the rpms were kept up.

Next day same thing. But I accelerate off a stop sign and the rpms are jumping up and down, I then coast off to the shoulder, and await my tow back to the shop.

I was positive it was a bad fuel pump so I switched it out with a new one.

Still nothing its not even trying to start. Dont seem to be alot of fuel pressure while cranking, I just get a little squirt out??

Check for spark and nothing?

So I tap the coil and some other things, not really knowing what im doing at this point. Try to start it and it hits and runs really rough for about 15 seconds and then shuts back down.

SO I replace coil, pickup oil, and the little computer modgule thing.

Crank it, and still no spark out of the coil and not much fuel pressure.

So I pull crank sensor, I brought it to the little garage in my town and he hooked it to a volatage meter and told me it was open. So I put it back in but still nothing.

I am pretty much stumped here. I would like to do further diagnosing. I dont much for testing equipment so bare with me on this. I got to get this back on the road soon so I just want to thank everyone in advance..

paxfam1

[muddog321]

Heres a start:
1. Check the fuel pressure at the valve on the fuel rail - KOEO 60psi is the min to start. Fuel filter changed - if not do it (under frame rail by drivers seat.
2. Done the crank sensor and still no spark at the coil so check to see if 5v feeding the coil with key to run and voltmeter on the 2 outside pins in the coil connector (unclip it and test in the connector.
3. Could be ignition module but need a scan tool to check and they are $80.
4. Check all fuses inside and out - eng and 2 ecm ones.
5. Replace the dist cap and rotor before you go for the ign module - just had one internally arcing and no way to tell without changing - yes believe it.
6. Cam sensor does not stop stratup only idles rough so thats not it.

[paxfam1]

Fuel filter was changed but no diffrence,

I only seem to be gettting the fuel thats primed when the key it turned, after that the pump doesnt kick back on

the ignition modgule was replaced earlier but it didnt make a diffrence


I will check for the 5v tonight and post the results

[Blue Bowtie]

Does the pump not run again for two seonds when the engine is cranked? Bump the key briefly to move the engine and listen for another two-seond pump cycle.

[paxfam1]

Well, the fuel pump is working as so.......When I turn the key it primes and when I bump it primes again then I think it must hit a sertain presssure and then when I bump it it doesnt run any more, but if I let the squirt of gas out it will work again.

As far as power goes, as far as I can tell there is no power to the coil at all, but there is power to the little ign modgule I beleive thats what it is, but I replaced that so it should be good. Should there be constant power to the coil while they key is at run and not just when its cranking??

Also I noticed the alternator was making a high pitch humming, I thought maybe something was wrong with it so I unhooked it but it still dont start.

What should I check next, shouldnt there be spark coming from the coil, even if the distibutor cap or somthing was bad, I mean I replaced the pick up coil, but seems like even if something was off time or something I could at least get it to hit once, but no.

Where do I go from here?

[paxfam1]

People, could I please get some ideas on where to go from here, I really would appreciate some help.

Thanks in advance

paxfam1

[paxfam1]

Well, the fuel pump is working as so.......When I turn the key it primes and when I bump it primes again then I think it must hit a sertain presssure and then when I bump it it doesnt run any more, but if I let the squirt of gas out it will work again.

As far as power goes, as far as I can tell there is no power to the coil at all, but there is power to the little ign modgule I beleive thats what it is, but I replaced that so it should be good. Should there be constant power to the coil while they key is at run and not just when its cranking??

Also I noticed the alternator was making a high pitch humming, I thought maybe something was wrong with it so I unhooked it but it still dont start.

What should I check next, shouldnt there be spark coming from the coil, even if the distibutor cap or somthing was bad, I mean I replaced the pick up coil, but seems like even if something was off time or something I could at least get it to hit once, but no.

Where do I go from here?

[Blue Bowtie]

The fuel pump seems to be operating when it should, but we still don't know what the pressure might be. There has to be a minimum of 61 PSIG (I've seen them start at 58, but barely).

[paxfam1]

At this point, if I could figure our why I have no spark I would damn happy

lol I really kneed some pointers..................

[blazes9395]

Alright, I have read this one, sounds interesting. The Ignition module has been replaced, also the crank sensor has been replaced too. I have too look tomorrow for the diagnosis chart for this one. I had a similar problem like this on my '95. Turned out being the connector to the ignition module was not good, and was intermittent and caused me a lot of trouble. When checking for spark, hook up a spark plug wire and ground it to the block, don't just check for spark at the coil itself, you run a risk of damaging either the coil, or more importantly the ignition module again(happened to me and I needed to warrenty the first module I bought because I damaged it, also took me awile to firgure out I cooked the one I bought). You have to make sure the ignition module is getting the right voltage, with the key on engine off, and also while turning over the engine, same goes for the crankshaft sensor. I don't remember the correct flow chart for diagnosis, so I have to find it.

[paxfam1]

That would be good if that was the problem, the only reason I was testing for spark from the coil was to elimante any problems in the dist cap/rotor. But yea if you could get me the specs that would be great!

[Macgyver007]

Just one side note, If you have a MAF on your rig (which you would on a 98) once you open the throttle body (take the rubber boot off) it will run bad untill the air intake is put back on. I had a Problem with mine it was esentially a vacume leak around the top of the boot. Mine would start NP, run like A_S. but rechecked what I had done a week before and the boot had shifted and was not locked in correctly.

[paxfam1]

No its not that, I cant even get spark it wont even attempt to start so thanks anyways!

[blazes9395]

Alright, a easy way to check if your ignition module and or crankshaft sensor is operational is when turning over the truck to start it, you should have your tach working, or if you don't have a tach, you need a scanner where you can watch live data. If the scanner shows rpm, ( 200-500 rpm), when turning it over, then at crank sensor is operational, as is the module. Also, what is the status of your battery? Does it have a sufficient charge?

[paxfam1]

It seems as if the rpms quit, when I removed the crank sensor. I had it tested and it was open so I put it back in and now it does not show the rpms going up or down. Yes the battery is charged up, also I noticed a whining noise coming out of the alternator so I unhooked it but it made no diffrence!