Opinions on a good fuel pump.

daddystang · Jul 14, 2008

What kind of success have you guys had with which fuel pumps. Please give your opinions. Thanks...

I'm looking to order a new one.

HISSIN50 · Jul 14, 2008

Walbro is the OEM supplier and who most of us use for replacement or larger pumps.

That said, your BBK was probably a repackaged Walbro, and you questioned how well that one held up for you.

(If the car runs fine once running, I would not assume the pump is bad. You could still have an issue with the prime-out, FPR, an injector, or check valve).

daddystang · Jul 14, 2008

Thanks Hissin for the reply. Now my question is how do I narrow down which of those possible problems you mentioned could in fact be the problem. I'm looking at as my fuel pressure guage does not show pressure when I turn the key to on. Wouldn't that point to the pump? Sorry if that sounds like a dumb question. I've just been trying to track down this problem since last summer. Please keep your ideas coming.

Mr. Rustypwnz · Jul 14, 2008

walbro gss 340

HISSIN50 · Jul 14, 2008

Did you try cycling the key several times?

Alternatively, ground the FP terminal on the self-test connector so you do not have to cycle the key. Or jump the common and Normall Open fuel pump relay terminals. Or supply fused battery power to the pump.
I'd want to get the pump to prime for 10-20 seconds before ever cranking to see if pressure ever builds.

If the car runs just fine, and FP is in spec while actually running, the FPR is probably ok. To test it, you can carefully use a fuel line crimping tool to restrict the return line. This deadheads the fuel system in case the FPR is bypassing all your fuel back to the tank. If your pressure all of a sudden builds (when it would not before), you're onto something.

Another possibility is a leaky injector or rail. You'd probably have issues like smelling fuel, seeing it puddle or having hard starts [fouled plug(s)] when hot (when the car would sit overnight, the fouled plug could clear after pressure bleeds off, which is why it starts ok in the morning).

I still have the feeling it is either truly not priming properly (power the pump with fused battery power directly to confirm this) or the check valve is bad.
That's just my postulating however.

Good luck.

daddystang · Jul 15, 2008

Yes sir I did try cycling the key several times, and it did not build pressure.

I will ground the FP terminal on the self test connector today for 20 seconds to see if pressure builds. If none builds, what does part do you think that points to as being that culprit so I can get the new part ordered. I'm hoping to have this corrected by the weekend, and I appreciate all your help Hissin.

The car does run pretty well, and holds fuel pressure very steady so I'm thinking the FPR is ok.

I've checked all the plugs recently, and none showed any signs at all of being fouled.

I don't have a fuel line crimping tool.

daddystang · Jul 15, 2008

Hissin, I was running my problem by a friends mechanic today, and he made a few suggestions some of which are right along with what you are saying. He doesn't think it is the fuel pump, but rather maybe the fuel pump relay or eec relay. He mentioned the FPR, unti I told him that it holds pressure when it is running. Could the relay be "going" bad. I thought they either worked or they didn't, but I'm no expert.

You've mentioned before the prime out. What do you mean by prime out, and what exactly is the check valve?

I will probably grab a relay on the way home today and try it. If it's not that, I won't be upset having a new one anyway. I've done some searching on here, and it seems when people have had bad relays their fuel didn't run at all which is not the case with mine.

Just throwing some thoughts out there.

Thanks for any continued assistance.

daddystang · Jul 15, 2008

Here's a really silly question, but one I have to ask. If my fuel filter was on backwards could that cause my problem. The reason I ask is when I replaced it about 2 years ago I got pre occupied while changing it, and guessed when I put the new one back on. Could someone tell me which side of the car the arrow on the filter points to. The drivers or passenger side. Thanks...

HISSIN50 · Jul 15, 2008

The only difference in the FP relay circuit that I can think of when priming out vs idling is that the battery voltage is higher while idling. Otherwise, the circuit functions the same way.

Priming or prime-out: When you turn the key on and the pump runs for 2-6 seconds and then turns off. This is a preprogrammed period of time that the EEC runs the pump to build adequate pressure (the pressure is not monitored however). If something is wrong, it takes multiple primings or extended cranking to get the pressure to build to 40 PSI.

There's a check valve in the pump assembly. It allows fuel to flow forward but not back into the tank. If this valve gets weak, it can take extra time to charge the fuel line. The FPR is what is supposed to bleed pressure off once you shut the car off (you dont want the lines pressurized for no reason. Aftermarket FPRs tend to bleed off much faster than OEM reg's).

If grounding the FP terminal in the STC doesnt build pressure, the last test I would do is to run a fused jumper wire from the battery to the pump. If this makes the pump go like crazy but it wasn't before, you'd want to dissect the wiring further.

I cant remember which way the filter is oriented. The filter has an arrow and it's pretty obvious which line comes from the pump and which one goes towards the front of the car. I can see how having it on backwards could create issues, especially once it begins to fill up with debris.

daddystang · Jul 15, 2008

I just got done checking a few things.

First-the filter is on correctly so scratch that.

Second- I had my wife watch my FP guage while I cycled the key again, and this time I did it about 10 time, and this time it did build pressure to between 40 and 50 psi. Then slowly dropped off so that's a good sign.

Third- I tried to ground the fuel pump test port on the test connector, but could not get the pump to run at all. Does this tell me the FP relay is bad?

Thanks Hissin again.

daddystang · Jul 15, 2008

Update:
I must have been doing something wrong at the FP port on the SCT connector, because I tried it again, and this time the pump ran, and the pressure went up very quickly to 50 pounds. So now I'm stumped.
I can cycle the key about ten times, or trick the pump at the sct connector both build pressure. But, turning the key one time does not build pressure. I don't think it's my pump. I think the problem is before the pump. I checked the fuse panel, nothing noticeabley bad there.

I noticed I had already replaced the relay once already, because I found the old Ford one on the shelf.
Any thoughts out there.

HISSIN50 · Jul 16, 2008

The pump should pressurize the line within 2 prime-out periods (about 10 seconds of having the pump run).

Because the car runs fine, there is no logical conclusion that I can reach. If the ground strap in the EEC was on the outs, the car would lose pressure while driving (the EEC grounds that same wire that you grounded).

I honestly cannot draw any reliable conclusion from the testing.

At this point, I would try another angle. Put a DMM on the normally open terminal at the FP relay (should be dk green/orange on your car IIRC). As soon as you turn the key on, you should see 12 volts. Every time you turn the key on, boom, you should see 12 volts here. If you do, one can assume the wiring to that point is ok.

daddystang · Jul 16, 2008

No problem I'll check the wiring today after work.

Thanks Hissin.

I'm just as confused as you are. Thanks for hanging in there with me. Hopefully this will help someone else later on.

LX302 · Jul 16, 2008

Hmmm,
When my pump died, it would start most times, but then other times it would let me sit.
I had to "prime it" key on and off a couple times before the pump would kick on and start the car. Once running, if was fine.
This was back in the day when I forgot to change the fuel filter for a while and basically burned the pump out.
So an intermittent start could very well be the pump.
Can you get your hands on a used pump to test?

daddystang · Jul 16, 2008

Thanks LX302 for the response.

I don't have a spare pump to try. I want to exhaust all other options first before I go and order a new pump, because the pump does prime, or at least I hear it run every time I turn the key. I just can't get it to build pressure on the first turn of the key for some reason.

daddystang · Jul 16, 2008

Hissin I checked the voltage at the relay, and at the grn/orange wire I got 1.245 or 12.45 volts ( my meter was acting up and it's a Fluke). At the red wire I got 12 volts with the key on. I think that was the 12 volts you were looking for. So I think the wiring is good.

Before I did anything I had my son turn the key on for the first time of the day while everything was cold, and I watched the guage. Much to my surprise it built 30 pounds of pressure. I'm going to let it sit a while and check it again. What do you think is the fuel pump getting heated up after driving for a while, and maybe causing problems with the check valve or something. Then after sitting and cooling down it is able to build pressure on the first turn of the key again.

Just a theory. What do you guys think?

HISSIN50 · Jul 16, 2008

daddystang said:
Hissin I checked the voltage at the relay, and at the grn/orange wire I got 1.245 or 12.45 volts ( my meter was acting up and it's a Fluke). At the red wire I got 12 volts with the key on. I think that was the 12 volts you were looking for. So I think the wiring is good.

Before I did anything I had my son turn the key on for the first time of the day while everything was cold, and I watched the guage. Much to my surprise it built 30 pounds of pressure. I'm going to let it sit a while and check it again. What do you think is the fuel pump getting heated up after driving for a while, and maybe causing problems with the check valve or something. Then after sitting and cooling down it is able to build pressure on the first turn of the key again.

Just a theory. What do you guys think?

I'm not sure we tested the correct wire. Red is the EEC relay input on the control side of the relay.

In lookin at the wiring diagram, dk green/yellow still appears to be the power output to the pump.

Be aware that lt blue/orange (similar looking if the wires are faded) is the ground for the relay's control side.

daddystang · Jul 16, 2008

I think I did test the correct wire and did get the 12volts we were looking for. I guess my meter was just freaking out a little bit. What do you think about the pump buidling pressure when the car is cold on the first turn of the key? Do you think it could be heat built up in the pump causing the check valve to stick? Thanks

HISSIN50 · Jul 16, 2008

Because of the differing results in the testing, I'm not able to draw any conclusions.

A pump on the outs often will fail or get weak when it gets hot. You don't have that problem.

Because the issue only arises while priming, I would still attack the wiring side to be sure the pump is seeing 12 volts. It will make noise with less voltage but the fuel volume moved is considerably less. The red wire is not the output to the pump (that output wire the only wire we care about at the fuel pump relay).

If the pump was failing, you very well should have seen lean codes, but our self-diagnostics might not pick up on something that acute.

I would still be checking FP relay output voltage or even using a fused jumper to the pump to see if it will charge the rail hard each and every time you power it up yourself.

daddystang · Jul 16, 2008

So to be devils advocate lets say my meter is working correctly and I did see 12 volts at the green orange wire. Where should I go from there.

On the other hand lets say my meter for some reason had the decimal point in the wrong place and did read 1.245 volts. Does that mean I have a bad point in that wire somewhere. If that's the case I wouldn't think the pump would'nt build pressure even when cold.

I'm not completely electrically inclined, maybe that's why I keep steering back toward something mechanical like the pump, but I am trying to follow your advice. You seem to have a methodical way of diagnosing this problem which I appreciate rather than just saying sure pop on a new pump and see what happens. Thanks..

Just not sure where to go from here. The meter read 1.245, but the graph under it read 12 volts. Not sure which to believe. I guess the reading. Why then would I only be getting 1.245 volts?

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