Troubleshooting / Chugging, stalling, Fuel pump?

Hey all,
I was out wheeling at night and all was good. Once we got back on the pavement I tried pushing on the gas to accelerate up to speed (55mph) and it wouldn't do it. I pushed harder on the gas, and the engine's RPMs didn't respond at all. Didn't notice ANY problems on the "trails", but as soon as we got to pavement, it acted up.

I eventually got it to the wheeler's house and parked it for a few hours after switching relays and having it run fine.

On the way back, it started giving out. I'd push the gas and either nothing would happen or it'd chug. It was fine while coasting most of the time. Pulled over and switched to a different relay. Didn't fix it.

Any ideas?

From other forums I was thinking either Fuel Pressure Regulator or the Fuel Pump. Both the Fuel Filter and Fuel Pump were replaced a year or two ago (Less than 15,000 miles).

It's currently parked a block (downhill) from my house, so some quick help would be awesome. Don't want it towed to an impound lot (again). It stalled barely off the road. It would start... chug... and die after several seconds of 'feathering' the gas pedal to try and get it going.

I don't have a Fuel Pressure Gauge. The Fuel Pump still appears to prime when the key is turned on... but doesn't appear to be as loud as it previously was. Before I could hear it prime from inside, now I can only hear it if I have my head under the exploder.

FYI: I have a 1994 Exploder 4.0L V6 4x4

Your problem sounds similar to what my '92 did earlier this summer. Part of the problem was a vaccum hose had come off. The other part of the problem was a fuel filter. The first thing I did to diagnose was to put a fuel pressure gauge on it, and I could immediately see that the pump was only generating 15-20 psi (engine needs at least 25ish to run properly).

In the absence of a fuel pressure gauge, I'd probably pull codes from the computer (see my notes on pulling EEC-IV codes if this is new to you), check for vacuum leaks, and other basic checks. I don't know that you can get a complete diagnosis of this without a pressure gauge, though. IMO, if you want to DIY modern EFI engines, then you need to have access to a pressure gauge, because almost all of them use a pressurized fuel system, and the only proper way to diagnose them is to be able to check the pressure.

FWIW, pressure gauges aren't expensive. Harbor Freight sells one for ~$15, though I can't vouch for the quality because I've never used one. The gauge I have cost ~$40, and can be found at Autozone and other similar places.

Would that be feasible, though? For a fuel filter to go bad after ~2 years of use and less than ~15,000 miles?

I had a Fram fuel filter put in... by a trusted mechanic.

Okay, so I borrowed a Fuel Pressure Gauge and got a reading. I also pulled the codes.
The only code that came up was "565", which has been the cause of my check engine light for quite a while.

With the fuel pressure gauge, 'priming' the fuel pump would get me around 20PSI. While running it would get around 30PSI... and then after running for about 45seconds to a minute I could see the pressure continually drop, and the engine would stall out.

Those pressures aren't high enough. I would say the filter is not the problem, if it drops once running like that. Since it's always low even when off, I'm going to say that you're fuel pump already failed again.

If you got it from Autozone or someplace similar it probably wasn't the best quality. You're best bet would be to spend a little more and try and get a new Motorcraft pump.

Edit: Also, did you install a full pump/sender assembly when you replaced the fuel pump? Or only the physical pump itself? I ask because if the strainer is not replaced with the pump it could cause problems.

okay... I was just out playing around with it making sure my previous post was correct. Everything was correct, but this time the engine kept running for a good 20+ seconds with the fuel pressure at Zero before stalling. When I tried to prime the fuel pump again, nothing happened. ($%#$).
Read the codes again, and now I'm getting 565 and 542 (Fuel Pump Secondary Circuit Fault).

I forgot to add in my original post that the relay for the fuel pump was quite warm in comparison to the others.

Now it won't start at all...
The fuel pump isn't that old, I don't see why that would be going bad already.

Ideas?

Try and replace that relay, maybe it wasn't connecting good. That would explain why it got hot, and why the pump wasn't priming all the way.

Edit: Wait-or did you already replace it once too?

devilboy222: I didn't "replace" it but switched out a relay with another one in the power distribution box that was the same.

Supposedly, the mechanic replaced the entire fuel pump/sender assembly as it had rusted through and I was leaking gas and/or gas vapors from the top of the tank (could smell it from walking by the vehicle). The business advertises that their parts come from "Auto Value".

After letting it sit for a few minutes (enough time for me to come in and use the computer), I can turn the key and see the pressure gauge go up to 20psi again... maybe the relay had to cool down?

I'm going to check to see if maybe the wires got damaged and are shorting out.
Any other ideas?

edit: can't find the wires...heh.

With the fuel pressure gauge, 'priming' the fuel pump would get me around 20PSI. While running it would get around 30PSI... and then after running for about 45seconds to a minute I could see the pressure continually drop, and the engine would stall out.

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That almost exactly what mine was doing. I decided to change the filter (probably ~2-3 years Fram) before changing the pump because it was a lot cheaper and easier, and the engine started going again. I could see your problem being from a clogged filter, and I believe that it is possible for a 2 year old filter to need changing (might have got a dirty tank of gas from somewhere or who knows what).

Probably worth the effort, especially with the 542 (CM or KOEO or both?) to put a voltmeter at different places in the fuel pump circuit and make sure the pump is getting a steady +12V. A varying voltage or less than ~10-11 V could indicate a problem in the circuit (maybe a relay as suggested) that is preventing the pump from running at full steam.

I could also see this caused by a weak pump. And sometimes the aftermarket pumps don't last as long.

Another possibility (though I think it's down the list a ways) is a bad FPR. If you can do this carefully, disonnect the return hose from the FPR, run the pump, and see if gas is being returned to the tank when the pressure is low. If the FPR is opening too early, you would get low pressures like that.

94 explorer

Please help me as my wife and i have no money to throw at this thing, it dies for no reason. it kind of chugs out of air or gas. then it wont start like its flooded, but if I pop the hood jiggle everything under the hood it might start but half the time it stalls out even if I feather the gas as it chug,chug,chug at 1000 rpm or under. is there any quik fixes I can try? a fuel addetive or any thing,like clean my filter, and how. pluss my fuel guage sticks at a 1/4 tank and that is allso when it is empty. any help is much appreciated. thanks for your help

richardnoggen said:

Please help me as my wife and i have no money to throw at this thing, it dies for no reason. it kind of chugs out of air or gas. then it wont start like its flooded, but if I pop the hood jiggle everything under the hood it might start but half the time it stalls out even if I feather the gas as it chug,chug,chug at 1000 rpm or under. is there any quik fixes I can try? a fuel addetive or any thing,like clean my filter, and how. pluss my fuel guage sticks at a 1/4 tank and that is allso when it is empty. any help is much appreciated. thanks for your help

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Start by checking for missing vacuum caps/lines. Then check fuel pressure and check for fuel in the vacuum line to the fuel pressure regulator (FPR). You might pull codes from the computer to see if there are any clues there.

....When was the last time the fuel filter was changed???...:scratch:

...From your description though, my guess would be fuel pump or FPR,,

I replaced the fuel filter... Though simply connected, it was horrible to replace. First tool I bought worked like crap, and the second I bought (the plastic kind) worked great... but still took a while.
Long story short. It still won't run.

When turning the key on (KOEO), I don't hear the fuel pump turning on anymore. It's not the Relay. I think the Fuel Pump died. I'm gonna check to see if it's still under warranty. I hope it is...

...Some times it's the electrical connections at the fuel pump...

Im new to the explorer world but I have had this problem with other vehicles that I own. Where the electric fuel pump starts to die out and then eventually becomes completely dead. It starts off with good pressure but then after the electric motor runs for a bit the motor gets tired. Then the next time it will get tired a little faster, the next time a little faster, and then eventually nothin.

Heh, Found the paperwork for my Fuel Pump. I've only driven 4,000 miles!!! Talk about pissed...
It's been a year and 4 months since it was replaced... it's my winter vehicle, so it doesn't see much driving. My entire Fuel Sending Unit was replaced because it rusted out and was leaking gas out of the top of the tank.

So... from this, I don't recommend anyone purchasing a Carter brand Fuel Pump (Part# P74123).

**rant** Unless I got swindled, which I don't doubt. They tried telling me my rear brakes had to be completely redone because my brakes were really soft. I took it apart and looked at it. They had taken a part out of it to show to me, and never put it back after I told them not to redo the brakes. So, I barely had any brakes driving home cuz they left out the self-adjuster thing. All it needed was like two springs and that adjuster... and they were in prime condition. (This is NOT the "Trusted Mechanic" I may have mentioned above).

So, after my XplorR sat in the drive for about a month, I finally was able to get it towed to the Ford Dealership to have the problem diagnosed and fixed. Turns out the wires are 100% A-okay. They determined the problem to indeed be the fuel pump.

I called Deforge Auto that had installed the fuel sending unit and fuel pump 4,000 miles ago and they would be more than willing to help if the warranty guys were willing to reimburse them for cost of the fuel pump.

Needless to say, The fuel pump people are strict on their 12-month, 12,000 mile coverage and wouldn't warranty my 16-month old fuel pump with only 4,000 miles on it.

There goes another $160 for the fuel pump plus 2 hours worth of labor down the drain. Ford is replacing it with a genuine ford (motorcraft) fuel pump, which is actually less-expensive than the piece of crap one I got that died which cost me $184.

We'll see how things are when I get it back from the shop on Wednesday. If I don't post again, everything works great. If I do... obviously something else is wrong.

(BTW: The explorer still occasionally starts. For some reason, it likes cold weather and will actually run for like 5 minutes in it. It's odd, from what I hear, for the thing to still start if the fuel pump is bad)

I'll also be looking over the old fuel pump, making sure that Deforge Auto actually did replace my fuel pump with the Carter fuel pump (Yea, I really don't trust them...)
Any ideas on how to tell the brand/model of a fuel pump? I've never really looked at one before.

buy a bosch pump from advance auto...comes with a lifetime warranty for around $130 .i bought one and over 15k later no problems.

boggs1227 said:

buy a bosch pump from advance auto...comes with a lifetime warranty for around $130 .i bought one and over 15k later no problems.

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Unfortunately, I live in the boonies and the nearest Advance Auto is... too far away (we're talking like a 2+ hour drive). Shipping would take too long, as snow is on its way here and I need the 4-wheel drive to get around. If it weren't for the steep hills I have to climb every day, I'd consider it. To get up the hills in my car in the winter normally takes me spinning the tires at around 70mph while only moving up the hill at around 5mph - but only after getting a good 30mph worth of momentum at the base. Without the momentum, you just slide back down the hill.

Thanks for the suggestion, though!