2000 454 fuel probs...

[Chuck L.]

Inherited a problem, that I can't ID.
2000 Chevy 3/4HD.
A used truck, that has had this problem since 2nd owner has had it.[He bought it w/ 160K on the odometer. Now at 236,000]
Truck starts easily when cold.
Starts easily, if restarted very soon, after warmed up.
Has prolonged start time, [say 10 secs of cranking], if it is allowed to sit for, say 10 minutes. When it does start, it throws black smoke, and nearly raw fuel out the tp's.
Clear flood helps to shorten the cranking time, and the resulting smoke show.
The long block was replaced in Jan 08, but the top end was off the orig engine. [@Approx 230,000 mi.]
GM tech scanned and said his findings were inconclusive. He did replace 1 inj.
New plugs, wires, fuel filter, have been put in. No cure.
I hooked up the scan program,[V2] and find:
A. A/F is constantly fluctuating from 2+, to 50.
B. Timing retard is constantly fluctuating from 2* to over 20*.
C. Idle is smooth @ approx 725.
D. IAT reads about 95*. Ambient was 75*.
E. Only fault code was for steering input theft det. Shown as "HC". I cleared the codes, and this 1 reset immediately.
MAP is steady at 36KPA.
**I found an air leak at the cleaner elbow. The mass air was dirty, so I cleaned it. No change.
**The owner changed 2 temp sensors. No change.[NAPA brand].
**The owner does not know if the O2's have ever been changed.
**Knock sensors are out of original long block. Maybe overtorqued??
I have a download of the tune file, and a datalog, but will have to have DFE1 post them, as my wireless router is on the fritz..

Now, the ?...
NE suggestions as to where I begin???

SORRY for the "editorial"!!

[joecar]

Chuck,

Commanded AFR is fluctuating... PCM is computing the airmass wrong...

If in CL, the this would cause the trims to be wrong...

Commanded timing is determined from cylinder airmass...

Ideas:
- O2 sensors;
- ECT sensor;
- MAP/MAF;
- leaky injectors;
- leaky fuel pressure regulator (diaphragm ruptured);
- IAT sensor looks like it may also have a problem.

Don't take the customer's word about what sensors were replaced, and don't assume the new senors are good.

It's not long, it contains all the relevant info...

[N0DIH]

#1 issue on these engines. Fuel Pressure Regulator. This is the EXACT problem I wrestled with for a long time. I refused to go on a parts swapping binge. I won't do it. To costly and fruitless. on FullSizeChevy.com we have seen a lot of people with and a 100% success rate of people with the same symptoms.

ONLY test that you can do is to connect up Fuel Pressure Gauge, pressurize fuel system, shut it off and if the fuel pressure drops down in a few min, even 10 psi, get the FPR out. Mine litterally had fuel puddled up in the intake it was so bad. I was seeing LTFT -18% almost always. And nothing short of 50% E85 would correct it. And still wasn't running right, but ran better. Now I run E85 (100%) and see mpg better than I got with gas and the bad FPR. Go figure, it was bad....

They are notorious for leaky injectors, toss some in while you are at it if you can. You can SEE if they leak when the upper plenum is off, just fire up the fuel pump once you have the FPR replaced or before, and look at the tips, you can see them on the L21/L29 454.

But the FPR is almost always the issue. You will see fuel come out the fuel line when it is disconnected, but you cannot get to the FPR or vacuum line without the upper plenum off.

Do the FPR first, and get it Autozone, it is the IDENTICAL part at NAPA, only NAPA charges 30% more... I bought both and even the boxes are the same size with the same printed label on the side.

Check out FullSizeChevy.com, we have a lot of BB threads running, this is one of them. I am on there, look for posts for FPR and 454 in the techincal forum.

Don't go into the craze of replacing parts blindly (JoeCar is right on the list I was working on testing on mine, he is for sure there on the right track), I did the O2's on this one and got some crap ones in there that are fussy, and my GM ones are still good (put one back in). Get GM sensors if you REALLY want to replace them. The key for them over non GM (AC Delco) is GM requires the SHELL to be grounded to Sensor Low, most aftermarket are NOT. Connected up a wire manually got my aftermarket sensors to work. I was ready to live a life of Open Loop over this thing, but fueling was still too ugly with the bad FPR...

It will gain significant more power and drivability, as well as mpg. You'll love it....

http://www.fullsizechevy.com/forums/...-starting.html

[Chuck L.]

THANKS guys, for the help!
I'm on my way to fullsizechevy, now..

I just registered and read that thread.. LOTS of good info on that site!!
THANKS, again.

[Chuck L.]

THANKS guys, for the help!
I'm on my way to fullsizechevy, now..

I just registered and read that thread.. LOTS of good info on that site!!
THANKS, again.

Have been shopping for parts.
Have:
Fuel reg, filter, plugs, gasket, air cleaner element, batt cables.
Went to the "stealership", to get the air cleaner elbow. Ran into the "Goodwrench tech" that had worked on this truck.
He had some interesting "feedback".
Says the truck is JUNK, and not worth fixing it.
He said the problem was the timing, and a bad inj. He checked the injs, and found 1 leaking. [Replaced it]. He then returned the next nite, and had his timing lite with him.
He said timing was off 2-3*. He reset it to the factory spec of "0", at idle. The truck was running just fine when he left.

What do you guys think? Should I look elsewhere, since those items are now "OK"??

[joecar]

Check the FPR...

Key on several times to build pressure, the FPR has to hold pressure, if it doesn't then it or the inj's may be leaky;

if you remove the ait hose to the FPR, it should not have any gas in it, and with a vac hand pump it should be able to hold vac.

[N0DIH]

Well worth fixing for sure. The 454 is an animal tuned and with good injectors/FPR. BRUTE force for sure. Sure a 6L or even a 5.3L might beat it in a drag race, but you won't stand a chance with 10K or 12K on back....

I have towed 10K with mine (99 Burb 454) and it was very much at home towing heavy and got 9-10.5 mpg towing (even cold out with a bad FPR at the time!).

Hard to test them FPR's, one they have to have the intake off to see them, and 2, you can't get 4 bar with a vacuum pump, mine tested perfect and 100% the same as a new one on the bench, but leaked gas out the line. 4 bar vs -0.7 bar isn't the same. I think mine was good to 20-30 psi, still in the near 2 bar range or over.

Yeah, the timing offset needs to be right. My LT1 I think can set for it software, but the L29/L30/L31 need it be dead on.

Can you test that with EFILive?

[97K15004WD]

He had some interesting "feedback".
Says the truck is JUNK, and not worth fixing it.

Sounds like he is trying to buy your truck!!

[N0DIH]

sorta what I was thinking!

Sounds like he is trying to buy your truck!!

[hquick]

Yeah......

And yes, you can check the timing with EFILive...log GM.CMPRET.