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No fuel pumping

wwwylie

New Member
Joined
June 3, 2002
Messages
7
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0
City, State
WI
Year, Model & Trim Level
'98 XLT
Looking for some clarification for testing a fuel pump. I have a 98 4.0 SOHC that doesn't want to start. The engine turns over fine, but no ignition. The fuel pump isn't kicking in. Checked the fuse, fuel pump relay and the PCM relay. All test fine. My question is, the relay connector does not see the couple seconds of power for the pump. What does that mean? I am thinking a bad PCM or connections to/from it. Any advice?

I have the Haynes manual, but it doesn't go into what the test means.

I am obviously hoping it isn't the fuel pump.

I am selling the truck just because of its age (166k) so now it is acting up. I also had to replace a leaky oil pan. The truck is stuck out side and it is about zero so I want to do my homework before doing the actual work. :usa::exp:
 



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Wiring diagrams

I have the wiring diagrams for my 2000 Sport. I've read that there were significant wiring changes in 1998 so your wiring should be very similar to mine. In 1999 the fuel system changed from a return system with a fuel pressure regulator (FPR) mounted on the fuel rail to a returnless fuel system with the FPR mounted in the fuel tank and a fuel pressure damper mounted on the fuel rail. However, I don't think there were any significant wiring differences.

If you want, I'll be glad to help you troubleshoot your fuel problem. The exercise will help me to expand my fuel pressure test procedure. Do you have a multimeter and are you familiar with using it? Do you have an Owners' Guide showing the location of fuses and relays? Please be specific about the symptoms and what you have done so far and learned. Also, please be exact in following and reporting the actions I suggest. Otherwise, I will end up following an incorrect wiring path and we will waste a lot of time.
 






Testing

StreetRod Thank you for the offer to help.

The basic problem is no start.

The fuel pump does not pump when the key is turned to on.

I check the inertia switch. OK
I checked the fuel pump and PCM fuses and I checked both relays for function on the bench. All OK.

There is power at the fuel pump relay connector, but none of the terminals have the momentary voltage with the ignition switch being turned on. That is a test in the Haynes manual, but they don't explain what it means if you done get it. The obvious is you don't get the pulse of the fuel pump when the ignition is turned on. The fact that I am not seeing anything at the relay is giving me hope it isn't the fuel pump.

I then got to your tests

1. Does "THEFT" blink rapidly with ignition key in Off, On or Start?
Yes: Verify key validity - Yes
Check Passive Anti-Theft System (PATS)
No: Go to next numbered step

2. Check fuel tank gauge reading. If fuel possibly contains water or condensation from cold add treatment to the tank. The truck as been sitting most the winter, the tank is low and it is prime condensation weather (5 F yesterday 30F today). I don't think that would cause the Fuel pump not to pump.

3. Turn ignition key to On
Does "CHECK ENGINE" illuminate? Yes
Yes: Go to next numbered step
No: Perform the PCM Power Procedure

4. Turn ignition key to Start
Does starter motor crank engine? Yes
Yes: Go to next numbered step
No: Perform Starter No crank procedure

5. Does "CHECK ENGINE" illuminate while engine cranks? Yes
Yes: Check CKP sensor How do you check the CKP? I only have an old ODB-1 scanner handy. I can borrow a newer one but not till tomorrow.
No: Go to next numbered step

6. Check inertia fuel shutoff (IFS) switch is set (button pushed in). OK

7. Check battery voltage OK

That is where I am at. I am also checking all the connectors and ground for the PCM and pump.

8. Perform TPS Test Procedure
 






Let's back up a little

While I was waiting for you to respond I started an expansion for my fuel pressure test procedure. Since it sounds like you don't have voltage when you first switch the key to On I'd like to back up to that point before pursuing the CHECK ENGINE light staying on when cranking. First here is some background information to aid in your understanding how the system works:

"Fuel pump electrical procedure

Background

The energizing of the Fuel Pump Relay is controlled by the PCM. If the PCM does not have power then neither will the Fuel Pump Relay. The Inertia Fuel Shutoff (IFS) switch (located next to the front passenger kick panel) prevents the fuel pump from receiving power after a collision. The main power to the Fuel Pump Relay comes from Fuse 9 (20 amps) in the Battery Junction Box. The PCM energizes the Fuel Pump Relay for a few seconds when the Ignition Switch is turned to On and when the Ignition Switch is turned to Start. According to the Haynes Repair Manual the PCM monitors the Camshaft Position Sensor (CMP) to determine if the engine is turning and deactivates the Fuel Pump Relay when there are no CMP reference pulses. However, more than one forum member with the V8 has reported that the engine will start and run (although not well) with a defective CMP sensor."

And here is where I am in the procedure expansion:

"Procedure

1. Turn Ignition Switch to On
Does "CHECK ENGINE" illuminate?
Yes: Go to next numbered step
No: Perform the PCM Power Procedure

2. Do you hear the Fuel Pump run for a few seconds when Ignition Switch is switched to On?
No: Go to next numbered step

3. Is Inertia Fuel Shutoff (IFS) switch set (button pushed in)?
Yes: Go to next numbered step
No: Depress IFS reset button

4. Check Fuse 9 (20 amps) in the Battery Junction Box

5. Swap Fuel Pump Relay in the Battery Junction Box with the Rear Wiper Down Relay in the Battery Junction Box and repeat step 2 above.

6. Disconnect Fuel Pump/Sending Unit electrical connector (C311) located on the inside of the left frame rail in front of Fuel Tank.

7. Is the resistance from female C311, Pin 7 (black wire) to ground less than 1 ohm?
Yes: Go to next numbered step
No: Clean/tighten the ground connection (G204) located under left side of Instrument Panel behind Kick Panel.

8. Is the voltage at female C311, Pin 6 (pink/black wire) battery voltage for a few seconds when Ignition Switch is switched to ON?
Yes: Remove/replace fuel pump
No:
 






We have ignition.

Street Rod
Thank you again for all your thorough explanation.

I am happy to say I got her running. I am even happier I don't have to tackle that fuel tank.

I pretty much had it narrowed to the PCM but couldn't figure out the cause. T figured I try the PCM and then move tot he crank sensor since the PCM is easier. I pulled the PCM & blew out the connector. I also pulled the ground strap and scored it pretty well. I then turned the key, didn't hear the pump, but went on to crank it and the theft light was off so I knew it did something. I shut it off then on again. This time the pump turned over. When I cranked it, both lights whet off and she started right up.

What does the check engine light while cranking tell you?
And what does the flashing theft light tell you?
Both were on when cracking and not starting.

In your procedure I'd check for the ingition on voltage at the realy for the fuel pump. That should tell you if the problem is before or after the relay.

The tech procedures you and the others on SE are really helpful. I am still amazed by the guy who figured out the radio display fix. Thanks again and keep up the good work.

Know anybody in WI who wants to buy a 98 with 166K?
 






Congratulations!

I'm glad to learn that you got it started and thank you for posting the solution!

The CEL while cranking is one of the few indications of a faulty crankshaft position (CPK) sensor sometimes called CPS. It is a very difficult fault to identify.

A rapid flashing THEFT usually indicates an invalid key in the ignition. However, with PCM power problems there's no telling what might happen.

Thanks for the tip on probing for voltage at the fuel pump relay. My goal is to order the steps to achieve rapid isolation of a failure with the least effort/complexity. It's an ongoing process improvement with inputs from people like you assisting greatly.

Good luck on selling your vehicle!
 






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