# 2001 8.1 starting hard..



## Mick76 (Aug 2, 2009)

Heres the deal, 2001 94K just had the spark plugs replaced.... they were the original ones and my mechanic broke off 3 of them trying to get them out..... he managed to get the 3 broken ones out but now when the truck is cold or has been sitting for 15 minute or so , I'll go to try and start it..... all I get is the engine turning over. bring the key back and try again and it starts (sometimes hard sometimes pretty easy)....... Would a bad or soon to be bad crank sensor be the problem ? anything else I should look at?

TIA
Mike


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## BowTieDmax (Nov 25, 2003)

crank sensor


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## B&B (Nov 4, 2006)

Was or wasn't the hard starting issue there before your mechanic replaced the plugs? What plugs did he use? Brand and p/n?


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## Mick76 (Aug 2, 2009)

BB...good questions... not a problem before i had them replaced but its a truck i don't drive that often (8.1 gas mileage and all) and I thought about the plugs being the wrong ones but it seems every little thing happens to this truck!...its been a big pita.....
I'll find out the brand and pn for you


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## Mick76 (Aug 2, 2009)

BB... He went with the Bosch OEM plugs from napa


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## B&B (Nov 4, 2006)

The 8.1's are fussy about plug choice and Bosch is one they're never happy with therefore will cause misfiring, hard starting, rough idle etc. AC Delco 41-983's gapped to .050 (not .060) are what you want to use in any 8.1 regardless whether any issues were there previously or not.


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## Mick76 (Aug 2, 2009)

Thanks BB... I did just reverify the plug choice and he did put in the ac's like you mentioned above but with the .060 gap... i'm bringing it to him to have him regap and see where that takes me...thanks again!


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## brad96z28 (Aug 21, 2005)

B&B;1315188 said:


> The 8.1's are fussy about plug choice and Bosch is one they're never happy with therefore will cause misfiring, hard starting, rough idle etc. AC Delco 41-983's gapped to .050 (not .060) are what you want to use in any 8.1 regardless whether any issues were there previously or not.


I have replaced tons of the crap single tip bosch platinum for misfires. Never the double tip or +4. Not saying there good either. Delco are best in a gm. Sounds like possible fuel pressure though never seen new plugs start hard misfire yes. What does it do uf u cycle the key 2 or 3 times before u start the truck ? Try that and see if it starts normal then.


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## B&B (Nov 4, 2006)

Mick76;1315214 said:


> Thanks BB... I did just reverify the plug choice and he did put in the ac's like you mentioned above but with the .060 gap... i'm bringing it to him to have him regap and see where that takes me...thanks again!


If he used the correct plugs just tightening up the gap .010 won't fix it, there's something else going on.

You're still not clear on whether the issue was there before hand so I can't give you an accurate prognosis but if it didn't have the issue beforehand have him check the intake duct at the TB and MAF to be sure he didn't dislodge it while working under the hood or to be sure he re-installed correctly if he had it removed. A small air leak downstream of the MAF will cause a hard start.

If is WAS there beforehand then there's only a couple things that can cause it on an 8.1. An air leak in the intake duct as previously mentioned, lack of fuel supply while cranking or a faulty CKP...although they almost always manifest themselves with a stall once underway, not a hard start but it can happen.


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## Brian Young (Aug 13, 2005)

Mike, I had the exact same problem with our 00 GMC. It had a 7.4L. I change plugs with the ones recommended, changed everything you could think of and same thing. I was at our Fisher dealer and we were talking about it, he said their lot truck did the same thing and they removed the throttle body and cleaned it very well and problem solved. He said they've done that to many other trucks, same type, same issue, (they're a garage as well). I did a quick cleaning, basically sprayed some throttle body cleaner stuff in there and it helped but then we sold it. The crank sensor in ours checked out ok while that issue was still there.


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## larboc (Dec 8, 2009)

your IAC is dirty


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## B&B (Nov 4, 2006)

Brian Young;1315491 said:


> Mike, I had the exact same problem with our 00 GMC. It had a 7.4L. I change plugs with the ones recommended, changed everything you could think of and same thing. I was at our Fisher dealer and we were talking about it, he said their lot truck did the same thing and they removed the throttle body and cleaned it very well and problem solved. He said they've done that to many other trucks, same type, same issue, (they're a garage as well). I did a quick cleaning, basically sprayed some throttle body cleaner stuff in there and it helped but then we sold it. The crank sensor in ours checked out ok while that issue was still there.





larboc;1315638 said:


> your IAC is dirty


Both good tries and are two items that should be cleaned annually on any truck (although there is no IAC on a 8.1 so don't search for it too long) but neither will cause a hard start on an 8.1, only a rough and/or unstable idle. Drive by wire works differently than cable operated throttle body and will easily overcome a dirty throttle plate during starting.


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## Mick76 (Aug 2, 2009)

B&B;1315482 said:


> If he used the correct plugs just tightening up the gap .010 won't fix it, there's something else going on.
> 
> You're still not clear on whether the issue was there before hand so I can't give you an accurate prognosis but if it didn't have the issue beforehand have him check the intake duct at the TB and MAF to be sure he didn't dislodge it while working under the hood or to be sure he re-installed correctly if he had it removed. A small air leak downstream of the MAF will cause a hard start.
> 
> If is WAS there beforehand then there's only a couple things that can cause it on an 8.1. An air leak in the intake duct as previously mentioned, lack of fuel supply while cranking or a faulty CKP...although they almost always manifest themselves with a stall once underway, not a hard start but it can happen.


Didn't have the hard start issue before changing the plugs...... Mechanic was thinking fuel since if I cycle the key before starting it , it seems to start right up no problem but he'll look around for the other things mentioned.....thanks again and I'll post the findings once he figures it out!


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## 496 BB (Feb 11, 2010)

Did he change the wires? I know those are VERY sensitive to breaking and Ive done that to more then a few since they can be a royal PITA to get loose even with grease on em from last time. Wait till you see the price on em too. I went MSD last time.

Id check the fuel pressure before anything. Mine went out with no warning at all but Ive had some go out starting with hard starts. If it runs good after you start it I wouldnt think it was that or plugs. Sounds like air intake is loose or sensor not plugged in on it. My damn K&N pops off the the TB all the time creating this problem.


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## djagusch (Oct 15, 2007)

I would ask how he got the 3 broken ones out? Could he of bent the valves getting them out? Could he left some material in the combustion chamber making the seats not seal or rings wear quickly.


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## Mick76 (Aug 2, 2009)

Well, my mechanic scanned for codes and found a faulty knock sensor which he replaced... he checked fuel pressure and all was fine.... i dunno.....


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## REAPER (Nov 23, 2004)

Mick76;1317741 said:


> Well, my mechanic scanned for codes and found a faulty knock sensor which he replaced... he checked fuel pressure and all was fine.... i dunno.....


Did that fix it?


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