8.1 liter sucks

[Mr.Pink]

I have an 8.1 in a 2001 3500. The problem i'm having with it is that sometimes it will just shut off. Sometimes it will shut off then start back up and the times in between it shutting off and starting back up differs. We've hooked up the computer and it doesn't show any problems. What could cause this? My engine doesn't really suck I was just trying to draw attention to this post.

[SlamChops]

crank sensor?

[millerxc]

sell it to me and don't worry about it , just the motor though.

[Mr.Pink]

Just changed the crank sensor about 4 months ago, and didn't really help.

[gilraine]

ignition control module???

[SlamChops]

yeah, the icm can certainly cause that too. when you say the 'computer doesnt show you any problems' does it just not have any codes or all the data looks correct? i've noticed at times on other gm's that when using the scan tool the rpm signal will either stop at a certain point (well below where it actually is). usually caused by a crank sensor. is it keeping fuel pressure? fuel pressure regulator maybe?

[hybrid-theory]

i had the same problem with mine, after i did a spark plug change... i wanted the bosch platnium4 and thats what i put in it, ran like shit all the time, gas milage was gone, stalled all the time out of the blue. so i took it down to the dealer twice, and on the second time they said it was the spark plugs.. i was very hesitant to think that was it, so changed them with ac-delco platniums, and holy shit it worked. they also said might of damaged a couple of plug wires too, so changed two of them at $22.95 a piece. i was glad a friend of mine worked at the same dealer, because he said there is alot of bulletins on this motor. not sure what computer you used to check it but, my friends didn't tell me anything, that was helpful, so thats why i took it to the dealer.. hope this helps.

[SlamChops]

workin at an auto shop where the owner used to work at the dealer, i dont put anything but delco plugs in my gm's now.

[JJS]

it's something to do with the ignition. experience tells me it has something to do with it being too far advanced causing the piston to expand when hot. creates too much resistance for the starter to crank it over. these guys are telling you it's one of the ignition sensors and i'm sure that's what it is. your best bet would be to have it scanned and see if its putting out any codes. otherwise you will have to go on hunches and might waste some money on parts it don't need.

[Mr.Pink]

That makes sense,the icm because when it dies it has fuel pressure. I will take it by my machanic and have him scan it again. I didn't know it even had a icm? Why did trucks get so complicated?

[DSBANHEN]

If you put an aftermarket cranksensor in it that might be the issue. GM has an updated cranksensor for this engine. It has no ICM. the pcm is the icm, and it runs all the coils separately. Either the pcm is losing the crank reference, or the wiring somewhere is rubbed through. also possible that the ign sw is going open, or a gnd is loose. good luck db

[Mr.Pink]

I don't remember what kind of cranksensor I installed and I'm going to check out the switch also. I beleive the problem is linked to one of those areas. I guess I was right when I said I didn't know my truck even had an icm. It's good to know that there are intelligent chevy people on this forum thanks for the info DSBANHEN

[mbryson]

I've had a battery terminal loose that caused similar issues on a GM computer controlled vehicle. Of course, the whole thing just died, radio, dope lights, engine, etc. but it might be worth checking out.

[3/4ton62gmc]

Dont know if you got it fixxed yet. But at the dealer i work at we were replacing 4-5 crank sensor a month for this problem. We have had some vehicles that had repeat crank sensor failures, so a bad sensor is not out of the question. Also double check to make sure the sensor is installed all the way it is possible to install the retaining bolt but have the sensor all the way in. Theres a GM bulletin on this problem.

[fastrexxx]

Sorry to bring up an old thread, but did this ever get fixed? I'm having the same issues with new new tow rig.

[fastrexxx]

Well, mine was a bad Crank Position Sensor. The dealer als replaced the computer and fuel pump as well, but the CPS fixed it.

[BLUE VEIN THROBBER]

i want a 8.1 in my truggy

[PAINLESS]

The engine will shut off if the oil pressure suddenly drops or the engine is getting low on oil, and usually will not restart till it cools off. A friend of mine had this problem with his 8.1. Mine uses about a quart between changes, especially if I have been doing a lot of towing.