Feels like fuel problem
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Instructor
Joined: Jun 2002
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From: Escondido CA
Feels like fuel problem
Tested the fuel pressure today 41 key on eng off--37-38 running --47 with vacuum hose off the regulator. Sounds about right? The problem I am hunting is it feels like its running out of gas over 3500 rpm. Some times it stalls above 3800 on a wot blast and takes about a min to restart (just like it ran out of gas). All the tune parts are new including filters. Checked the tps for giggles and its .54 at idle. I am stumped on this one. I have heard that maybe my valves are floating, but that wont cause a hard start after it stalls --the 2 are def related. Any ideas??
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From: SE NY
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Re: Feels like fuel problem (xzvs)
Lets assume the fuel filter has been replaced.
On the restart, check fuel pressure. Also, lay the gauge on the windshield, held by tape or a wiper blade, so you can monitor fuel pressure at the failure point.
Sometimes the three contacts just under the fuel pump mounting flange become corroded and simulate a fuel pump failure. I saw Gordon Killebrew fix a "failed fuel pump" at Carlisle last year by cleaning them.
If not for the restart problem, I might suspect clogged cats as the WOT problem cause.
Of course ignition problems can cause a problem at WOT as RPM go up. Typically in the form of faulty wires or fowled plugs.
When my MAF died recently it gave no codes, surged at idle and wouldn't take throttle even at low rpm, so I don't think your problem is in that area.
You might check to see if there are any stored codes.
On the restart, check fuel pressure. Also, lay the gauge on the windshield, held by tape or a wiper blade, so you can monitor fuel pressure at the failure point.
Sometimes the three contacts just under the fuel pump mounting flange become corroded and simulate a fuel pump failure. I saw Gordon Killebrew fix a "failed fuel pump" at Carlisle last year by cleaning them.
If not for the restart problem, I might suspect clogged cats as the WOT problem cause.
Of course ignition problems can cause a problem at WOT as RPM go up. Typically in the form of faulty wires or fowled plugs.
When my MAF died recently it gave no codes, surged at idle and wouldn't take throttle even at low rpm, so I don't think your problem is in that area.
You might check to see if there are any stored codes.
Thread Starter
Instructor
Joined: Jun 2002
Posts: 177
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From: Escondido CA
Re: Feels like fuel problem (65Z01)
Ok-- will have to check for codes. The fuel filter is new as are the cats. The only "old" tune part not changed was the wires. It doesn't feel like wires tho unless they are all failing at once. I may slap on some new ones here as I have to take the car to vegas from San Diego here on the 8th of next month, and would like for it not to kill in the desert. I too read the dirty contacts article and do suspect that a bit --but have to hold off as my tank is full at the moment.
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Joined: Dec 2000
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From: SE NY
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Re: Feels like fuel problem (xzvs)
Don't worry about a full tank. I had to install a new pump at work on Mesa, AZ just after I took delivery of my Vette two years ago and the tank was nearly full. Just have three vacuum nipples to cap those lines so they don't ooze fuel.
Anyway, check fuel pressure first to be sure it's the problem cause.
If you do wires, I suggest the TPIS wire set. They are hi-performance (and lower resistance than stock), fit stock looms, look stock and priced at $59.
Anyway, check fuel pressure first to be sure it's the problem cause.
If you do wires, I suggest the TPIS wire set. They are hi-performance (and lower resistance than stock), fit stock looms, look stock and priced at $59.
Thread Starter
Instructor
Joined: Jun 2002
Posts: 177
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From: Escondido CA
Re: Feels like fuel problem (65Z01)
ok I tested the tps wot voltage now that I have a spec. It was 3.74 till I realised the trans cable was too tight and not letting it go wot. Re adjusted and get 4.17 --is that still too low?? I heard 5v was wot. Also, could my trans cable saying wot and my tps saying not wot screw it up like that?
[Modified by xzvs, 3:22 PM 6/19/2002]
[Modified by xzvs, 3:22 PM 6/19/2002]
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Joined: Dec 2000
Posts: 90,675
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From: SE NY
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Re: Feels like fuel problem (xzvs)
Do NOT disregard the base idle TPS value!
You need to first get the engine to base idle, about 450rpm and then set the base TPS position. After that you can snug down the lower Torx and rock it to get the max WOT value (My method is on my site). Then you need to recheck the base idle value. A copla iterations usually gets the job done.
Note that you can set the base value to about .65Vdc and still not throw a code; that usually will happen if the base TPS value is above .67Vdc.
You don't need 5.0Vdc on the TPS for the ECM to recognize WOT; it's somewhere around 4.3-4.5Vdc.
You need to first get the engine to base idle, about 450rpm and then set the base TPS position. After that you can snug down the lower Torx and rock it to get the max WOT value (My method is on my site). Then you need to recheck the base idle value. A copla iterations usually gets the job done.
Note that you can set the base value to about .65Vdc and still not throw a code; that usually will happen if the base TPS value is above .67Vdc.
You don't need 5.0Vdc on the TPS for the ECM to recognize WOT; it's somewhere around 4.3-4.5Vdc.