Fuel Pump Resistor Location?

[Javakart31]

I have 2001 GP GT 3.8. Would like to know where the fuel pump resistor is located, if it has one. The threads I have read say that it used to be located under the front wheel well but since has been located to the rear of the vehicle in 01. Thanks

[BNaylor]

Originally Posted by Javakart31

I have 2001 GP GT 3.8. Would like to know where the fuel pump resistor is located, if it has one. The threads I have read say that it used to be located under the front wheel well but since has been located to the rear of the vehicle in 01. Thanks

The fuel pump resistor is only applicable to the GTP model since it has a high volume 2 speed fuel pump.

What specific problem are you having with your GT?







Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[Javakart31]

It's got 67000 miles. Problem has only happened twice over the last 3 months. It basically won't start after it had been run for a continuous time and it's hot. It's my wifes car, the first time it was towed but fired right up at the shop, no codes. We changed the fuel filter cause it was time.

Second time she had run it for about an hour in the pm, made a stop for 5mins and it wouldn't start. Waited 20mins and it fired right up again, drove it home (5 min drive) and I was finally able to experience the problem. Wouldn't fire, felt like no fuel delivery. Turns over but won't fire. It appears to be heat related as both incidents happened on very hot days after extended drives and short stops.

So now I have this car and my wife is driving my truck.

So I hunted around this forum and saw a few threads related to the fuel pump, pressure regulator and the resistor. It wasn't clear to me if the resistor was applicable to the GT.

Talked to my mechanic. He says the fuel pump on GMs can be problematic, but he doesn't want to guess. They're expensive to replace. Also mentioned it could be the crank sensor, a relay, wiring/connections or the computer. I'm going to try to recreate it and test voltage at the fuel pump to start. Any other ideas?

BTW, it's time for me to purchase a shop manual. Recommendations?

Thanks for the assistance.

[BNaylor]

On the GT or even a GTP, if you suspect a fuel problem then the best thing to do is have the fuel pressure tested at the fuel pressure regulator (FPR) Schrader valve. That way you could possibly rule out an expensive fuel pump job or the fuel pressure regulator. The pressure at the fuel injector rail and FPR should read in a range of 45 - 55 psi with 52 as a median reading.

Based on your symptoms, it could be the crankshaft position sensor (CKPS) too. Do you ever get a SES/CEL light?







Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[GMMerlin]

When your vehicle stalls and will not restart, you need to check a couple things. Fuel and spark.
Spark is the quickest and easiest, just pull a plug wire off the spark plug and place the plug end to a good ground (engine metal). Spin the engine over and you should have spark jump from the plug wire to ground. This is a waste spark system so check 1 wire from each coil 1-4,5-2,6-3
If you have spark there then you can concentrate on the fuel system. The correct spec for your vehicle is 53-59 psi.
It sounds like your concern is heat related and on those vehicles, the ignition system is usually what fails (either the CKP sensor or the ICM).
Usually a failed CKP sensor will not throw a code on these vehicles but will not send a RPM signal thru the ICM to the PCM.
You could have a loss of power or ground to the ICM which supplies the power and ground to the CKP and CMP sensors.
You can disconnect the CKP sensor and test the Yellow wire with a Volt meter to ground, you should see 10-11 volts.
If you have the proper voltage there, check between the Yellow and Black (wht tracer) with your voltmeter and you should see6-8 volts..if the test passes, the CKP sensor is the component that has failed
You will have to perform these tests when the car won’t start.

[Javakart31]

Thanks for all of the input.

No we have never seen the SES/CEL light.

I finally got a hold of a manual and a wiring diagram so once I identify where to physically measure, and can recreate the symptoms I may have a shot at narrowing it down. I will let you know what happens.

[BNaylor]

Originally Posted by GMMerlin

If you have spark there then you can concentrate on the fuel system. The correct spec for your vehicle is 53-59 psi.

I disagree. How so? What is the methodology? Is that with vacuum to the FPR disconnected or connected?????? I've never seen fuel pressure readings on any '97 and up Grand Prix reading above 55 psi when the testing is performed correctly.

Don't know if it will help the person with problems but here is the proper procedure to check fuel system pressure and test the fuel pressure regulator:

********************************************
Install fuel pressure gauge to Schrader valve on the FPR.

Remove vacuum hose from FPR.

Turn ignition to on (not start) and note fuel pressure reading on gauge.
Record reading.

Start engine and verify you feel vacuum at the hose end.

Reconnect vacuum hose to FPR.

Note fuel pressure reading again and record reading.

Now compare the first and second reading.

Fuel system pressure reading should be 4 -7 psi less with vaccum hose re-connected/installed. Fuel pressure should decrease as vacuum increases.

If results are not as specified, replace the fuel pressure regulator (FPR).
************************************************** ***

BTW - I just tested a 2002 Grand Prix GT with Series II 3800 and here what I got for readings and incidently the car runs fine.

At ignition on with vacuum hose off - 49 psi
Engine started and on with vacuum hose off - 53 psi
Engine started and on with vacuum hose on - 45 psi

And if you'd like pics I will be happy to post them.






Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[BNaylor]

Originally Posted by Javakart31

Thanks for all of the input.

No we have never seen the SES/CEL light.

I finally got a hold of a manual and a wiring diagram so once I identify where to physically measure, and can recreate the symptoms I may have a shot at narrowing it down. I will let you know what happens.

A defective crankshaft position sensor may or may not give a SES/CEL light. It's a real PITA checking the voltages and signals at the electrical connector to the CKPS but it can be done. We use a breakout connector at the Community College where I teach. Not only can we measure reference voltages easily but we can scope the outputs and timing pulses with an Oscilloscope.

In the event you find the CKPS bad, here's a procedure applicable to '97 -'03 Grand Prixs to replace it if you decide to DIY and save some money. Good luck!


http://mykidz.net/GTP/CrankPosSensor.shtml


BTW - Also check the electrical connector that plugs in the CKPS for corrosion or contamination. Clean with electrical contact cleaner (both plug and jack).







Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[Javakart31]

First thanks to both of you for the details. From my position all the info is relevant. My biggest problem is recreating the situation in order to trace it down.

What type of voltage levels do you see on the CKPS pulses? I'm assuming you ac couple to the signal line.

BTW I read this link and it was helpful in explaining the fuel delivery system

http://www.gmtechlink.com/images/iss...3e.html#story2

I also appreciate the forum.

[BNaylor]

Originally Posted by Javakart31

My biggest problem is recreating the situation in order to trace it down. What type of voltage levels do you see on the CKPS pulses? I'm assuming you ac couple to the signal line.

I agree that recreating the situation will be your biggest problem because it is intermittent. For one it's not that easy working around the crankshaft position sensor when the engine is hot. Then once the engine cools down and you start troubleshooting the problem may not be there. The other thing is how do you plan on monitoring the signals.

You do realize that GM uses sensors based on the Hall Effect principle?

Here's a basic description of a Hall Effect pickup:

A Hall Effect sensor is a digital triggering device that produces a square wave output that is processed by the Ignition Control Module (ICM). The digital square waves are in a form that the PCM will recognize.

The best way to monitor the output is with an oscilloscope. The signal will vary in amplitude. It's the frequency that's important. It's not the height or amplitude of the signal that's important, however, when the voltage from a Hall Effect sensor drops to zero that's when it fires the respective coil.

Here's the pin out for the connector at the CKPS:

Pin A - SYNC Wire = Lt. Blue/White
Pin B - 18X REF Wire = Yellow
Pin C - GROUND Wire = Black/White
Pin D - VOLTAGE B+ Wire = White/Black

Good luck!






Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[acre44]

I have a 1999 GT 3.8 NA and I just recently had the same problem you are experiencing. After I would run it awhile, especially on hot days, it would not start. If it sat for 15 minutes it would fire up. The problem was only intermittently, not every time, and NO CODES recorded. I changed the fuel pump and the Fuel Pressure Regulator and have not had any problem since. These cars have weak fuel pumps that wear out WAY TO QUICK!

[BNaylor]

Originally Posted by acre44

I have a 1999 GT 3.8 NA and I just recently had the same problem you are experiencing. After I would run it awhile, especially on hot days, it would not start. If it sat for 15 minutes it would fire up. The problem was only intermittently, not every time, and NO CODES recorded. I changed the fuel pump and the Fuel Pressure Regulator and have not had any problem since. These cars have weak fuel pumps that wear out WAY TO QUICK!

Acre44, just out of curiosity did you ever get error code P0440, EVAP Emission Control System Malfunction and the gas smell resolved?









Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[Javakart31]

Everything you wanted to know about Hall Effects

http://www.honeywell-sensor.com.cn/p...l/chapter1.pdf

docs are chapter1.pdf throught chapter7.pdf

BTW, Acre44 how many times did this happen before you went for the pump? Do you recall the frequency? Thanks

[acre44]

bnayler, yes I did figure it out. Seems the o-ring that goes in around the fuel pump is leaking. That thing is tough to get in, compress the pump and put on the c-ring. any tips on accomplishing this?

[Javakart31]

So I've been driving the car around trying to understand how I can recreate the problem reliably in order to troubleshoot it. It's been a while since I've driven it daily for an extended period and it just didn't seem right. Off the line it didn't have that torque that I remember. I dismissed it as bad memory on my part.

Well low and behold Sunday, after driving it all morning on a warm day I started up a fairly steep hill and decided to get on it a bit. Wham it fell completely flat, started to buck and jump, could only get to about 3k rpm and no further. Got it home and couldn't start it again, did some simple checks ie: spark, filters, relay. but turned up nothing. Next day it started fine but by the time I got to the freeway it barely could get on. It felt like a trans slipping or fuel restriction or maybe something related.... well I go home open my mail and read the nice service alert for the catalytic. Well no wonder this thing felt like someone shoved potatoes up it's exhaust. Needless to say I have scheduled a dealer visit.

If this does take care of it I won't tell my wife right away since this is a much better driver then my truck.