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88 GMC suburban craps out, now won't start

1K views 4 replies 4 participants last post by  68NovaSS 
#1 ·
HELP! I am about to lose my mind on this. Two days ago my 88 GMC Suburban started acting up: rough idle, puffing out black smoke, stalling when you touch the gas, strong smell of gas. Same day, a few minutes later, it started and ran as smooth as ever...for a little while. Still on the same day, little while later, acted up again. Next day, wouldn't turn over...just cranked. Replaced TPS sensor, fuel filter, and changed the oil (knowing that surely wasn't the cause...just felt good!) Few minutes later, started up, ran perfectly. Let it idle 5 - 8 minutes, shut it off, started right up again, idled fine, took if for a ride for about 10 minutes, stopping, starting, accelerating hard and soft - ran perfect. got home, shut it off, started it again, no problems. Half hour later, wife gets in to go somewhere, it acts up again...just like the previous day...sputtering, choking, black smoke, and then, after she touched the gas pedal, it died. Now today, cannot get it to turn over at all. Smells like gas when I crank it. Put fuel injector cleaner in gas tank, but, again, cannot get it to start. Today I tried a new MAP sensor...no change. I look inline and am so confused about what it could be: EGR valve, Air mass Sensor, Idle Air Control Valve, Fuel pump (which I can hear working when I put my ear to the gas tank opening), etc... ANY help would be unbelievably welcome!!!:confused: Thanks!!!
 
#3 ·
Sounds like a possible coolant temp sensor failure.Check the system for a CTS trouble code, code 15 , which would indicate an open circuit in the sensor or sensor circuit. If you get a code 15, put in a new CTS.then try it out. Its the easiest thing I can tell you to do. Its a pretty common failure.
If the problem is not code 15 related, it will be a mechanical issue.
TBI could be leaking through the regulator.Injector seals could be leaking also.
You need to verify that the problem isnt excessive fuel pressure also.
IIRC those tbi setups dont give a pressure test port. If it does then put a gauge on it. 13 PSI is where you want it to be.
Now its getting unmetered fuel from somewhere, be it the regulator is leaking intermittently, or an injector seal is leaking, or an injector staying open (stuck or ground circuit shorted to ground)
Also check the evap canister to be sure that raw fuel isnt making it past the liquid check valve in the tank to the purge valve and into the engine.
 
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