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took the battery down and had them charge it and put a load on it. It tested good. Got home put the multi meter on it and was 12.7 volts. hooked the battery up and it read 12.58 volts. Tried driving it in the field and of course it died. Connections did look a little worn ( bit of rust, I tried to scratch it out). may need to replace them as they are showing resistance by dropping the volts… Anyone agree 12.58 is too low while hooked to car.
Recap-lightning hit garage, truck wont start, I hear fuel pump startup when turning the key, checked fuses, re-paced relay- noluck, replaced coil and module bingo-Truck now starts. runs a short period of 2-5 minutes and dies. ODBII says cannot communicate. Battery test good. 12.7 on volt meter stand alone, 12.5 while hooked to car. 14 when alternator is charging. Engine is not missing, when it dies it just cuts off. When truck dies generally cannot start unless you wait a 30 sec to a couple of minutes. Idle seems a bit low at ~700RPM it does sound like it will die.
What else could lightning arc have screwed up? fuel Sensor, ECM, distributor & wires? Anyway to test these things by-passing the under dash OBDII port?
Need to logically walk back on this without throwing too much money at it..Did you check all your fuses? GM likes to use the cigerate lighter to power the DLC socket. If a scan tool will not connect to a vehicle, pin 16 on the connector is not getting 12v.
Did you ever try checking for spark with a ignition tester and fuel with a quality fuel pressure gauge when the vehicle dies?
As for the charging system, i would do a voltage drop test as well as checking your belt tension and the alternator field circuit.
Checked fuses replaced relay early on. Cigarette lighter lights up fine. OBDII port is getting juice I believe it said 14. negative drop test said .02 Does voltage drop need to be looked at? Gettting 14+ when running and no load, still dies. I don’t have a ignition tester or fuel pressure gauge available. the belts/tension and pulleys looked good.
Let me run this by you guys, I hear the fuel pump if I turn the key for about 3 sec. This morning and yesterday it ran about 10 minutes then died. So initially it runs longer then on next start ups it doesn’t last as long. That is telling me something is warming up causing it to die. Next the fuel pump, when running has a high pitch noise the whole time. I was listening under the car to the tank and the noise and car ended at the same time. Directly after it dies I turn the key off and back on to see if I hear the fuel pump, no noise, I try to start and just keeps turning over. I let it rest 30 sec and try again the pump makes noise for a couple seconds. I then try and it starts. Maybe lightning arc caused issue with fuel pump sensor or fuel pump? Does the high pitch noise of the F/P sound normal while running? Should the F/P start every time when turning the key to on, or would that cause a flood situation? Maybe I am barking up the wrong tree here.
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.
I really don’t see the point in testing the camshaft sensor yet if you can not verify if you have fuel or spark when the vehicle dies. And besides, the most effective way of testing those is with a lab scope.
Most auto parts stores will loan out a fuel pressure gauge and the ignition testers for spark can be purchased for around $10 if you have HEI ignition. Again all should be available from your local parts store.
Quoted From el_crab:
Battery tested good.
Just tried it and ran 5 minutes then just died. I was able to start right back up and ran 30 seconds then died. Then won’t start unless waiting a while, no smell of fumes. I hear fuel pump, checked fuse and pump relay.Just hearing the fuel pump running does NOT mean that it is good. I just had to replace one that I could hear running that I thought wasn’t the problem either until I put the pressure gauge on the fuel rail and found out that all that fuel pump noise only got me 9 psi to the rail instead of the 49 psi it needed. You may want to check the spec psi against what you are actually getting from the pump.
Much appreciated info. Good point dreamer. fuel/spark. I saw a video on checking f pressure, I will watch it again and hunt around my dads shop and or buy one. Then look around on where to hook it… These leads of encouragement give me can-do hope. Good point John, let see what gauge says and will update.
Thanks again.
Here’s a video on testing fuel pressure on a GM. GM was nice enough to put shrader valves on the fuel rail (as long as it’s not a throttle body injection, and I think they were gone by ’97):
http://www.youtube.com/watch?v=tJF5Lli4xq8
Are you saying that when the truck won’t start, you can’t hear the fuel pump run?
Ugg 50$ 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.
Back to Eric’s post last month. OBD2 just linked to other vehicles and cannot communicate with 97 sierra. Cannot find any blown fuses, pin16 has 12 volts on OBD2 port. I am with you PCM probably bad.
But, would it still run for a few minutes before it dies? Any videos on checking this or is it a high dollar trial. Should I avoid dealer mechanics? Advice appreciated.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?
Quoted From el_crab:
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?
In 96 they switched from the tbi engine to the vortec engine. so yes it is obd2. Sounds to me like you need a new computer. If ya happion to know a buddy with the same truck you could barrow theres. Just make sure its the same engine size.
I would locate a wiring pin out for the PCM and start checking your power and grounds. I would also check for a reference voltage on some of your sensors to see if the PCM is actually supplying the correct voltage for example.
99% of times, the PCM is not at fault.
But again, i would suggest loaning out the fuel pressure tool (you get all your deposit back) and see if your missing fuel or spark and continue your diagnosis from there.
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