1990 Chevy Silverado - turns over, but won't start - checked the obvious


tjivey
09-17-2012, 07:17 PM
OK, so I bought a 1990 Chevy Silverado with a 5.7L (350) TBI off Craigslist. I knew I'd have to do a lot to get it into shape, but now its kicking my behind. It was running a little rough and had very little power, so I changed the distributor cap and rotor. All good, but no real improvement.
So the next weekend I thought I'd change the spark plugs and wires. I gapped all plugs at .035 (as per specs), and replaced the plugs/wires one at a time so there was no chance of crossed wire confusion. Finished the job up and started the engine. It started normally and ran fine for about 1-2 minutes, then sputtered and died (almost like it ran out of gas). - I think I was reattaching the air cleaner at the time. Now it turns over, but that's it. It just won't start.

I did find a bad ground wire from the frame to body. I replaced the ground and cleaned all connections on ground and battery terminal wires. I also put a new starter and ignition switch in (with the broken ground wire, starter wouldn't fully turn over.)



I've checked the obvious.



I have power to the coil
I have spark (only checked at #1 plug wire, because I am working alone).
I have good fuel flow through the injectors
I have checked all fuses (that I know of - box under dash and on passenger side firewall under hood).
I have set the engine to top dead center (by crankshaft mark) and verified that rotor is pointing to plug wire #1.


I know I have to be missing something fairly easy. Someone please throw me a bone. I'm trying to get this thing running before my wife has it towed to the shop and I have to admit I made a bad purchase. Any help would be appreciated.

Thanks,

TJ

j cAT
09-17-2012, 07:48 PM
well the obvious to me would be replace the fuel filter.

cut open the fuel filter and see how bad it is/whats in it. rust/dirt/water ........

like you stated "sounds like it ran out of gas "

the TBI has 2 injectors when cranking are they dumping fuel ?

these vehicles have metal tanks with alcohol [water fuel] this creates lots of fuel filter plugging debris.

if it still is lacking start what does the spark look like when cranking ?

if no spark could be a spark module. not sure what was used on this old model .

aleekat
09-17-2012, 08:16 PM
I would try some starter fluid first, if it fires up, fuel delivery issue. If not, suspect ignition issue.

tjivey
09-17-2012, 08:24 PM
Sorry, I forgot to mention that the fuel filter was also replaced a couple of months back by the previous owner. Filter looks brand new and I found a receipt from Autozone in the glove box.

Fuel spray looks good. Same quality spray as when it was running well last week. I have tried spraying starter fluid with no luck, so I have to assume it's not a fuel delivery issue.

As for spark. I am working alone, so I was only able to test by pulling #1 plug wire and connecting a test light. I can see the test light flashing, but there is no way for me to tell the quality of the spark. If the spark control module (ECM) or ignition control module are bad, would it still show spark?

2000CAYukon
09-17-2012, 10:28 PM
I bought a 90 GMC brand new and was forced to sell it in 2010. It was a good truck but the tranny went out during a home remodel and I sold it.

My 90 would not start if the vacuum line to the MAP sensor was disconnected. The MAP is located behind the TBI. Be sure the vacuum hose is in good shape. Mine has to be replaced as the glue no longer worked and it leaked. If you have a vacuum pump, make sure the MAP can hold a vacuum or it needs to be replaced.

You can jumper the ALDL to see if there are any codes posted. Here is how to get the codes: http://www.troublecodes.net/GM/

Here is a list of codes: http://www.troublecodes.net/GM/89-90_57k.shtml

Post back if you find any codes and good luck.

//2000CAYukon

j cAT
09-19-2012, 09:25 AM
Sorry, I forgot to mention that the fuel filter was also replaced a couple of months back by the previous owner. Filter looks brand new and I found a receipt from Autozone in the glove box.

Fuel spray looks good. Same quality spray as when it was running well last week. I have tried spraying starter fluid with no luck, so I have to assume it's not a fuel delivery issue.

As for spark. I am working alone, so I was only able to test by pulling #1 plug wire and connecting a test light. I can see the test light flashing, but there is no way for me to tell the quality of the spark. If the spark control module (ECM) or ignition control module are bad, would it still show spark?

with this getting fuel then connect a wire to the distributor cap long enough to mount to a spark plug where you can see it when cranking. ground the plug base to the frame. connect the wire from distributor to the plug input . the spark must be blue. check the ignition coil, also the distributor pick up coil.

also the timing may be off. the timing chain could be broken.

with the cap off the distributor crank engine to be sure distributor rotates.

tjivey
09-19-2012, 03:36 PM
IT'S ALIVE!!! finally up and running again. Still a little rough, but I can work on that (more posts to come, I'm sure).

So it appears that even though I had spark, it wasn't good quality spark. I replaced the coil (no change), then the ignition control module (success).

Thanks for the input guys. I look forward to picking your brains again soon.

j cAT
09-19-2012, 07:18 PM
IT'S ALIVE!!! finally up and running again. Still a little rough, but I can work on that (more posts to come, I'm sure).

So it appears that even though I had spark, it wasn't good quality spark. I replaced the coil (no change), then the ignition control module (success).

Thanks for the input guys. I look forward to picking your brains again soon.

good luck happy to hear you fixed it. being that old those parts needed replacing any way. cap/wires /plugs ICM/coil............

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