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Dare I say ECM/PCM. My scan tool was saying cannot link on a 97 GMC with known lightning surge while sitting outside of garage. The fix was ECM Napa $116 (internet price) flash for $40. links now and works fine. The think that was throwing me was it ran for a few then cut out. and brake lights didn’t work until replacing EMC.
For you,
1. Error trying to link to computer,
2. No power to F/Pump. Relay changed. Fuses checked. (Does computer control relay to F/P?)
I don’t fully understand that system, wonder if you could run a hot wire to the F/P?But the coil doesn’t have power… Does the Fuse box have the correct voltage running to it?
Alright lets go ahead and close this bad boy out.
Broke down and took to a dealer and paid $45 to get a diagnosis. They also said ECM.
Had NAPA order it yesterday. $116. +70 core charge. They flashed it for $40 I provided VIN and mileage 218,000. I installed it started and ran good several minutes. I shutdown, hooked up the OBDII and put key in the on position. Bingo, immediately connected. No codes the brake lights now work. Started and it ran a long time without stalling. So this time…. I think I got it (knock on wood!) Thanks everyone for the comments. Hopefully, someone will find this useful, I know I did.
It’s good to get Dirty/right spark or fuel.
Lightning-module/coil replace. Now starts, but stalls.Generally when it stalls I turn the key to the on position and listen for the F/P. When i don’t hear it it usually don’t start. When I hear it it usually starts. I guess I could disconnect the F/P and put a meter on it to see if it gets 12v after it dies. feel like this is working backwards.
Since OBDII wont connect to PCM, how can I check that without resorting to Chevy Dealer?
I notice when I turn the key to the on position, truck not running, the oxygen sensors get really hot, is this normal?
Resolved:
Well Fuel pump replaced. Issue seems to be solved. no stalling thus far. The filter seemed to be pretty clear too. Interesting the Fuel Pressure didn’t increase. With the bad pump it was 53 and with the new pump and sender it is 52. Still out of specifications, but it is holding pressure now.My dad said the dealer charged him ~900$ to change the F/P, F/F ~6yrs ago. I’ll tell ya, those connections were sooo rusted I ended up twisting them off and had to get a new sender. I am skeptical the F/P was ever changed.
Anyway, thank God for the forums and videos! This has given the do-it your-selfers more tools and confidence. I think I learned more over the past couple of months on this than I did in 2 yrs of highschool autoshop back in the early 90’s.
Just when you think you got it…. Drats. Just died again. Guess I will check the voltage going to the f/p.
Yeah no connection to PCM.
Would a low voltage to the F/Pump cause low pressure? Or not to work at all? Also, if I am right about the F/P going bad, what causes the truck to die? Is there a sensor that kills it if there is low pressure, or should it run low pressure indefinitely? Cause it’s not sluggish’ing out it just cuts off and you stop hearing the F/P.
Any definitive way to test regulator? Does the theory below look correct?
Would it be more a regulator issue if:
I pressurize the line, and pinch the pressure line and pressure DOESN’T hold? Which would suggest a leak on the top side of the gauge?
TANK——F/P——F/F——(PINCH)—–GAUGE ——LEAK~~~REGULATORInstead:
FACT 1: I pressurize the line and it look like a leakdown into the tank from the check valve on the fuel pump. (This DOES hold Pressure on the gauge, suggesting the regulator to be good.)TANK——F/P~~~LEAK———–F/F——(PINCH)—–GAUGE—–REGULATOR
(also, FACT 2: Fuel pressure from pump to gauge is 53, which is out of spec 62-66.)
FYI, When I pinch the return line it leaks down, This test shows could be any of the three leaking F/P, regulator, injector.Good video. Yeah it would be nice to have the scope… Probably less expensive to do what you said and get dirty now. Got a F/P, F/F and screen for ~100
1. Not in specs. running at 53psi . Specs 60-66psi. for 1997 GMC sierra 5.7 liter
2. When I pinch the return hose, when the key is in the on position the pressure bleeds quick.
3. When I pinch pressure line when key is in the on position the pressure doesn’t bleed. I see pressure drop as I release the pressure line.Summary- failing fuel pump and bad check valve in the Fuel pump.
Anyone agree?
Any other ideas on what could cause the stalling after the lightning strike? F/P is ~6 yrs old. It runs for 3 minutes and dies. No F/P sound after it dies.
Just want to do due diligence before dropping $100 on F/P and F/Filter. Wonder could inadequate voltage to the F/P cause an out of spec condition for the fuel pressure like we see. Or if it would just fail to start period.Ok, dreamer your on to something. Got a F pressure tester that fits the Gm for 42$. Turn key to on position and goes to ~ 50 and drops in 2 sec when pump turns off. doesn’t hold pressure. I start it and sits right on 53psi. Specs are between 60-70. Same thing when it dies it drops and is down within 5 seconds.
Not sure where the F/P regulator is. The F/P was replaced in ’06’. The F/P relay was replaced after the lightning hit.
Any ideas on narrowing it down?Tag in the door says 96. I wonder if this is a OBD transition truck with what they call OBD 1.5. Any connections available that may be needed? Has anyone heard of this on GMC 96 vehicles? The tag under the hood said OBD compliant and DOESN”t mention OBDII. Any experience here on this fellas?
Rechecked all fuses. I do not see cigar fuse. (Cig lighter is working.) Double checked pin 16 on OBDII port it is getting 12v. CanOBD2 is the brand, maybe I need to update the firmware since this was purchased for this issue and haven’t seen it working yet.
http://www.truckforum.org/forums/attach … hfuses.jpg
http://www.canobd2.com/Known- Module and coil replace, now starts. Since this was hit by lightning I will assume it is electric component somewhere failing. I know, assume nothing. ‘
I need to locate the cam sensor and test it. Anyone know where it is? under the plug wires somewhere? Frustrating issue. Been going on since last summer. Either ready to get a tow truck and have dealer look at it. (don’t know any mechanics). Or, park it in the back of the field and let it rot….. Uggggg.
Much appreciated info. Good point dreamer. fuel/spark. I saw a video on checking f pressure, I will watch it again and hunt around my dads shop and or buy one. Then look around on where to hook it… These leads of encouragement give me can-do hope. Good point John, let see what gauge says and will update.
Thanks again.
Ugg 50$ for a pressure tester and 100 to rent one. WTF… Wish I could get the OBDII working to pull codes. I do see a double fuel line up by the coil with a blackcap over a valve, I think this may be the shrader valve.
No, truck will start and run fine 5-10 minutes then just die. Have to wait 30 sec- 2 minutes for a subsequent start. Or it will just turn over and over. Then when you wait and start it , it will run less time before it dies. Just like clockwork. This all stemmed from a lightning strike in the garage. Replaced module and coil to get it to simply start and here I am.
No haven’t changed the FF yet, Think it is an sensor something sensitive to that lightning that is causing this. Need to test so I am not throwing $ at unrelated parts.
