Fuel Pump Runs Erratically. Stalls. Code 41.

[HighMileage]

Maybe someone can tell me where to start looking here...

If I run 12V to that factory fuel pump wire behind the A/C compressor,the pump (a DW-301) buzzes quietly and maintains 42psi without the car running. Good.

But,yesterday I turned the key on and got 0psi. Of course,the car wouldn't start.

I turned the key on again. This time it made it to 30psi and started,stumbled along at 25mph and quit. FP gauge acting erratic.

It started right back up,but was running rough and threw a code 41 on the Scanmaster. Check engine light.

The car barely made it to my storage garage.

That's when I jumped the factory wire and got a steady 42 or so psi with engine off. So,my guess is it isn't the pump.

I do have a Hotwire kit I installed. (see sig)

Is there another relay besides the Hotwire relay? What should I look for?

Any suggestions appreciated.

 

[HighMileage]

Yup... Leave it to me to not get any replies. I'm not sure why. Hopefully my question is not a dumb one.

Here is what I'm thinking:

Take my existing Hotwire and run it in the car to a 30 (?) amp switch. That would eliminate any relay issues.

Just straight,fat wire to the pump with a high amp switch somewhere inside the car.

How about that?

 

[TexasT]

You could but then the pump would run ALL the time.
Do you have a meter?
If so, some basic trouble shooting is in order.
Does the relay receive proper voltage?
Did you pinch any of the hot wire? Look it over and see. What kind of voltage is the wiring getting to the back of the car?

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[HighMileage]

You could but then the pump would run ALL the time.
Do you have a meter?
If so, some basic trouble shooting is in order.
Does the relay receive proper voltage?
Did you pinch any of the hot wire? Look it over and see. What kind of voltage is the wiring getting to the back of the car?

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But it would run only when I switch it on,right?

I'm not sure what anything back there is getting. Gonna catch a quick nap and go check things out.

One thing is for sure,tho.. When I put 12V to the factory fuel pump jumper-wire behind the AC compressor,the pump runs flawlessly and puts out 42spi with engine off.

 

[RmvBfrFlght]

The fuel pump relay that is activated by the ECM is on the passenger side under the hood. It is located on the metal bracket on the fender.

Code 41 is a cam sensor error.

RemoveBeforeFlight

 

[earlbrown]

If the fuel pump runs fine when you install a jumper that tell you that everything from the relay back is good. Since you replicated the trigger to fix the problem that tells you that the issue is with the trigger part of the circuit.

The pump gets turned on (giggity) from two places... The ECM and the oil pressure switch. After the engine is running those two work in parallel to each other so the only way you can have a problem like your describing is if one of them fails and the other is flaky. Once the oil's idiot light goes out the pump should run with or without the ECMs input.

On your test where you turned the key on with 0PSI, if you would have cranked the engine until the oil light went out, pressure would have probably jumped up and fired the engine.


Since it seems like you're throwing oddball codes and having intermittent problems, I would get under the car on the DS and look up. Right there the steering column penetrates (giggity) the firewall, there's a pointed mounted screw that ever so slightly kisses the wiring harness at the back of the valve cover. See if any of the wires have damaged insulation. Then, while you're down there, make note of what screw it is... back it out, cut the pointed tip off, and reinstall.

 

[HighMileage]

If the fuel pump runs fine when you install a jumper that tell you that everything from the relay back is good. Since you replicated the trigger to fix the problem that tells you that the issue is with the trigger part of the circuit.

The pump gets turned on (giggity) from two places... The ECM and the oil pressure switch. After the engine is running those two work in parallel to each other so the only way you can have a problem like your describing is if one of them fails and the other is flaky. Once the oil's idiot light goes out the pump should run with or without the ECMs input.

On your test where you turned the key on with 0PSI, if you would have cranked the engine until the oil light went out, pressure would have probably jumped up and fired the engine.


Since it seems like you're throwing oddball codes and having intermittent problems, I would get under the car on the DS and look up. Right there the steering column penetrates (giggity) the firewall, there's a pointed mounted screw that ever so slightly kisses the wiring harness at the back of the valve cover. See if any of the wires have damaged insulation. Then, while you're down there, make note of what screw it is... back it out, cut the pointed tip off, and reinstall.

Excellent advice. I did turn the engine over for about 4 seconds when the FP gauge was at Zero. The pump never turned on.

Today I turned the key on and pressure jumped right up to 42psi. So something intermittent is going on here.

Honestly,I'm not liking all of this relay stuff. I see no reason for it at this point. I'm ready to run the Hot-wire into the car to a big,USA made REAL toggle switch. Maybe a household circuit breaker mounted in the ashtray!
...then out directly to the pump. No relays. I believe that is possible.

Not sure why it threw a Code 41. Maybe the engine was running so rough that something happened in the cam sensor?? ...or the ECM just got overwhelmed. It had about 30psi at the time. ...stumbling.

I'm gonna check that screw you are referring to tonight.

I ordered a fuel pump relay from Advance auto. It will be in tomorrow. $13. I figured what the heck.

Thanks for the reply.

 

[earlbrown]

The relay is working because when you trigger it yourself the pump runs.

I'd trust a 25 year old original relay over a brand new parts house china unit.

 

[forzfed]

Sounds like a bad relay, if that isn't the problem your ECM could be on the outs.

 

[HighMileage]

But wouldn't it cut the b-s out of the circuit to just have one big wire to the pump? ...with a heavy toggle somewhere in the car?

The ECM doesn't get input from the pump,so why even bother with this relay stuff?

I must be missing something here.

That switch sounds like a good theft deterrent,also. ?

 

[earlbrown]

The relay is to be able to pass large sums of current without the ECM having to handle all the load.

It's just an electromagnet and a set of contacts. They aren't as complex and finicky as they're made out to be.

 

[pacecarta]

check the ground for the OE fuel pump relay at the back of the passenger head

 

[TurboBuRick]

A relay is the same thing as a toggle switch except it it activated by power. Anytime allot of power is being drawn a relay is used to keep the load down on the control circuit.

Try this:

Pull the factor fp relay on the passenger fender and jump pin B and D with a small wire. The pump should run all the time with key on.

Maybe the factory relay is bad..


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[HighMileage]

First off,I'd like to thank everyone who helped me out on this. I *HAVE* to do this work myself. ...unless I want to tow it to Cottons an hour or so away.

I found the problem. ..hopefully. The factory relay is ok but is loaded with that old grease. I used contact cleaner and cleaned it a little.

**** The cam sensor plug wasn't plugged in all the way. (remember the 41 it threw once?) Maybe I didn't click it when I did the thermostat last year. Usually I'm good about that stuff,tho. I don't rush. When I found the loose plug,I let out a big "ah-HA!" (neighbors looked over)

After cleaning the relay, and doing the TurboBuRick test (test ok),I took it for a drive.

**All was good until I hit a big bump. Once back to the house,I started digging for "bump sensitive" loose wiring.

That still doesn't explain why I got 0psi of FP on startup that one time and the erratic FP.

Lets hope the cam sensor plug was IT! Pic:

 

[ttypewhite]

You might want to check your injector harness. If it's the original harness it probably gone bad due to its age. If you know of anyone who has a good harness for you to try, then you can see if that's the problem.