Old Problem Getting Worse, Time to Fix

Wags391 · #1 01-24-2010, 09:26 PM

1992 Chevrolet S10 Blazer, 4x4, 4.3L, "Z", 226,000 miles

Problem- Shutdowns. No fuel through injectors when trying to restart.

Notes- Fuel relay clicks when key is turned. Fuel pump is heard when key turned. If I remove the top of the air cleaner and look at the injectors, no fuel comes through when trying to start. This is for both injectors, so that leads me to believe that it's not an injector problem. After a while of trying to start, the engine eventually fires up. It is now worse than ever, taking longer and longer to start. Once the truck starts, it runs until I shut it off, except for some shuttering at stop lights and occasional dying at idle. No codes have been set.

Things I need to check- Fuel pressure, injector resistance... anything else?

Other advice, etc???

blazes9395 · #2 01-28-2010, 11:21 PM

Could be a few things.

Are you getting spark when it stalls?

Next, check and make sure the connections at the back of the distributor are tight. The ECM gets its reference from the distributor as to whether to fire the injectors or not. Start the truck up and wiggle the wires a little, see if you notice any difference when the engine is running.

From there, if you have a scanner, check and see what kind of readings you are getting from things like the coolant sensor, TPS sensor, etc, etc. Are you getting any codes that are popping up? The ECM in those years had a knack of going bad and acting funny. While the truck would still run with the bad ECm, it would do things like stall, run rich/lean/ poor performance etc.

Hopefully this gives you something to start at.

Wags391 · #3 01-30-2010, 07:55 AM

Quote:

Originally Posted by blazes9395

Are you getting spark when it stalls?
Next, check and make sure the connections at the back of the distributor are tight. The ECM gets its reference from the distributor as to whether to fire the injectors or not. Start the truck up and wiggle the wires a little, see if you notice any difference when the engine is running.
From there, if you have a scanner, check and see what kind of readings you are getting from things like the coolant sensor, TPS sensor, etc, etc. Are you getting any codes that are popping up? The ECM in those years had a knack of going bad and acting funny. While the truck would still run with the bad ECm, it would do things like stall, run rich/lean/ poor performance etc.

Long post, but want to give you everything I know...

I don't know about spark. Haven't thought about that. The way it was driving yesterday makes me think it might be that. It was sputtering badly during my two hour drive and when it would, when it kicked in there was a pop, as if there was gas in the chamber and the spark would come back and almost cause a backfire. I pulled over and while it was parked and sputtering, I looked at the injectors. Fuel flow seemed fine.

With wiggling the tires, do you mean see if the engine reacts?? My engine has bogged down for a long time while at idle and I turn the wheel. It's as if the power steering is taking all the power when I turn. Same with when I switch on the A/C. The engine bogs down, then picks back up. Sometimes it will do it continuously until I give it gas.

The distributor connections are fine. The distributor, with module, are new this last fall, but I haven't tested the module or the coil yet. I don't have a scanner, but I do have the ability to test the components (module, coil, TPS) with a DMM.

No codes have popped up, but last night oil pressure was a lot lower then normal, making me think I'm not getting the RPMs I should be. In the past year, I have gotten codes for the O2 sensor and a rich fuel mixture, but they go away. I have an extra ECM, so after testing everything I can, I will switch those out and see if it works.
Can you get an ECM reprogrammed? "Rebooted"?

blazes9395 · #4 02-01-2010, 08:28 PM

Quote:

Originally Posted by Wags391

No codes have popped up, but last night oil pressure was a lot lower then normal, making me think I'm not getting the RPMs I should be. In the past year, I have gotten codes for the O2 sensor and a rich fuel mixture, but they go away. I have an extra ECM, so after testing everything I can, I will switch those out and see if it works.
Can you get an ECM reprogrammed? "Rebooted"?

If you have a spare ECM, I'd give it a try and see if that helps. If the ECM is from a similar truck, or at least a 4.3, then it should just plug in and be alright. You can change the PROM chip from your ECM to the other ECM by removing the access panel and unpluging the one there and putting in yours.

Wags391 · #5 02-01-2010, 09:23 PM

Quote:

Originally Posted by blazes9395

If you have a spare ECM, I'd give it a try and see if that helps. If the ECM is from a similar truck, or at least a 4.3, then it should just plug in and be alright. You can change the PROM chip from your ECM to the other ECM by removing the access panel and unpluging the one there and putting in yours.

I do have an extra ECM and PROM, but I want to check everything else first to make sure all other components are working correctly.

Rick Norwood · #6 02-03-2010, 08:43 PM

When was the last time a tune up was done? Plugs, wires, cap, rotor? Start the truck and pop the hood open when it is dark. Do you see any blue arcing from the coil, wires or the dist. cap?

tom3 · #7 02-04-2010, 10:49 PM

My first guess would be the fuel pump, low pressure even though it's running. Hard to check pressure, have to cut a line or take off the filter and tie into it there.

Wags391 · #8 02-05-2010, 07:02 AM

Quote:

Originally Posted by Rick Norwood

When was the last time a tune up was done? Plugs, wires, cap, rotor? Start the truck and pop the hood open when it is dark. Do you see any blue arcing from the coil, wires or the dist. cap?

Plugs, wires, cap, and rotor are good. Haven't check for spark that way. I'll have to wait for when it shuts down again.

I will be checking fuel pressure soon. I found a tester that they don't have in the parts store. It's the Actron CP7817. It is specially for the TBI engines. It comes with an adapter that screws in between the fuel line and fuel filter with a schader valve on it. It allows checking the pressure with the fuel filter on and no disconnection of the lines at the throttle body. I'll let everyone know how it works once I get it. Ordered it off of Amazon. Same price as the one they sell in part stores.

Wags391 · #9 02-09-2010, 07:27 PM

Checked the fuel pressure. Over 15psi with all hoses connected, so higher pressure than spec. When I disconnect the return line, the pressure goes to normal, 9-13psi. What do I check next for blockage going back to the tank past the rubber hose?

Wags391 · #10 02-12-2010, 12:04 PM

Any tips on what to do about higher than normal fuel pressure, due to a blockage going back to the tank?

Wags391 · #11 02-19-2010, 10:23 AM

I figured out why I had high fuel pressure. The last shop to work on my tank pinched the return hose when the put the tank back up. Should be okay now. The hose has a crease in it, but it is allowing the fuel to flow fine as I now have spec fuel pressure. I don't know if this was the cause to my bad starts, but we'll see.

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