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How does a fuel pump break?

Killer Frogs

Full Member
Joined
Nov 5, 2007
Messages
317
Loc.
Amarillo, TX
Maybe a stupid question, but my engine starves for fuel. I've changed the setup with and without the accumulator and with and without the low pressure fuel pump, but it still pops at the air filter at times. So I'm wondering if my high pressure fuel pump might be bad.

So when a high pressure fuel pump goes bad can it be intermittent or would it just stop pumping fuel?

I'm sure it is not a bad ground, I added a Centech harness and the same problem was there before and after the new harness.
 

surfer-b

Contributor
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Sep 7, 2006
Messages
2,972
What is the fuel pressure gauge reading when this happens, if you don't have one this would be the first thing I would add. To your Q, yes the pumps can go bad but still run, that being said I havnt had one be intermittent (start and stop) but its possible, I have had them run but not put out the pressure it should.
there are few things that I can think of right away that may be the cause
1: loose wire + or -, I know you say you added new harness but just to make sure its not grnd run a wire from Neg battery post to the pump just to eliminate that
2: loose hose connection in the tank, if there is any in tank
3: if the pump is pulling through a filter or sock in the tank it could be clogged or collapsing

these are just a few things I can think of right away but you really need a gauge to chk the pressure when it starts to act up. I have never run the frame mounted system I always run the in-tank pumps, so others may give you better ideas on this system
 

PaveBronco

Sr. Member
Joined
Oct 30, 2012
Messages
912
prob, vapor locking due to heat. I always thought EFI couldn't, but they can, and I suffered through it until I finally said screw it and ordered an in tank set up.
the whole ordeal was miserable to troubleshoot because some folks never have a problem, even only running one high pressure pump. I even moved my TFI module thinking that could have been it, they can fail when hot and when cooled down act fine.
I really think that maybe one of my AN fittings was sucking air, but who knows. Where are your pumps and acc located?
 

Rustytruck

Bronco Guru
Joined
Feb 24, 2002
Messages
10,875
Is it possible you gas tank venting is an issue? might want to try it when its acting up and drive it with the gas cap loose or off. Just take it easy around the corners. You don't want gas all over your paint.
 

DirtDonk

Contributor
Bronco Guru
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Nov 3, 2003
Messages
47,354
All of those are good suggestions to check out Killer Frogs.
What else was done to the engine at the time of the re-wire? Was this all done at the same time the Explorer EFI was installed? Installed on a rebuilt flat-tappet engine, or a later roller engine?
Did you set your ignition timing by the book? Have you checked it since installing?

And last, is your EFI setup using coil packs or a distributor?

Good luck.

Paul
 
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Killer Frogs

Killer Frogs

Full Member
Joined
Nov 5, 2007
Messages
317
Loc.
Amarillo, TX
Hopefully I remember enough details. The motor is out of a 2000 Explorer. I stripped it down to the heads and rebuilt the top end. It is running the coil packs.

Garry aka efi guy rebuilt the engine harness and reprogrammed the ECU. Garry did hook up his laptop to my Broncos computer to check out the engine and he said he could not find anything wrong, that was when it was parked.

Jason at BC Broncos installed the Centech harness. After they did the wiring they were able to recreate the problem and said it was because my fuel filter was for a carb and they replaced it and had it running fine when I picked it up. The next day when I was 150 miles away the popping started again.

The popping is fairly constant when accelerating, 3-5 pops around 3000 rpm. Once I am cursing around 2000 rpm the pops stop, but the motor feels sluggish.

I don't think vapor lock is my primary problem. Sunday after doing a little re-plumbing, it was 65 degrees outside, engine was cool, and I went around the block. First time through the gears it popped.

My setup is basically the BC Bronco and WH accumulator setup. The fuel tank is one of Toms 23 gallon tanks. I run from the tank to a glass case filter, then the lower pressure pump, to the accumulator, to the high pressure pump, to a fuel filter, then to the engine. The accumulator, high pressure pump, and filter are basically under the drivers feet. I did replace the original fuel rail to one with a return line. The return line goes to a T on the accumulator, the other end goes to the vent on the fuel tank. On the fuel tank I am using the 2 metal lines that originally ran to the charcoal canister, but one line takes the return fuel from the accumulator and the other line goes to a vent mounted on the fire wall. At one time I removed the accumulator and low pressure pump, but had the same problem.

Most of the time it is just popping, but sometimes when it is hot it will get where it does not run well at all. The cure I have found when this happens is to burp the fuel line going into the fuel rail, almost like there is too much pressure. When it is trying to run before burping it, the fuel pressure gauge is jumping up and down. This does not happen very often.

I can get some pictures or part numbers if that helps in this mystery!

Thanks
 

DirtDonk

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Bronco Guru
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47,354
...The popping is fairly constant when accelerating, 3-5 pops around 3000 rpm. Once I am cursing around 2000 rpm the pops stop, but the motor feels sluggish.

Maybe someone else knows, or we can query Garry, but do these DIS setups also have a function that retards timing a lot while the engine is cold?
We used to have that problem a lot with wiring up TFI setups because any voltage on pin-6 (or whatever it was) at the TFI would fool the computer into radically retarding the spark. Made for some very sluggish running engines above about 2500 rpm.
Though now that I think about it, I'm thinking they would not even run above 3000 or so. Maybe not the same thing then.
If this was related to the issue, it might be a coolant temp sensor, or intake air temp sensor.

My setup is basically the BC Bronco and WH accumulator setup. The fuel tank is one of Toms 23 gallon tanks. I run from the tank to a glass case filter, then the lower pressure pump, to the accumulator, to the high pressure pump, to a fuel filter, then to the engine. The accumulator, high pressure pump, and filter are basically under the drivers feet.

I was trying to figure out how this could be causing problems when I read you saying that it happened even without the accumulator and low-p pump. Well bummer!
Still sounds like a potential fuel deliver issue though.

Did you happen to leave all the filters intact when you removed the accumulator? Maybe you're just suffering from a partially clogged filter, or filters.

I did replace the original fuel rail to one with a return line. The return line goes to a T on the accumulator, the other end goes to the vent on the fuel tank.

Why two return locations? Seems like it just introduces potential issues, where a single return point would be sufficient.
I think most do the "T" to the accumulator, but allowing it to all run back to the tank would theoretically let the fuel run cooler overall.
Cool fuel aside though, running to the accumulator would theoretically keep the supply of fuel in a more ready condition.
Not sure if there's an advantage to one or the other, or if both are even an issue. Just throwing out thoughts at this point.

On the fuel tank I am using the 2 metal lines that originally ran to the charcoal canister, but one line takes the return fuel from the accumulator and the other line goes to a vent mounted on the fire wall. At one time I removed the accumulator and low pressure pump, but had the same problem.

Do you notice the problem getting better or worse when the tank is full, vs when it's almost empty? Just wondering if the return line is causing too many air bubbles next to the fuel pickup area? Not sure it's a thing, and it certainly would not be when the tank is full. So if you get the issue when the tank is full, it would seem to not be a cavitation issue.

Perhaps as an experiment crimp down the flow of the return line. Using locking pliers, or better yet those specialty pliers designed to cut off the flow of rubber fuel lines while you work on the system. Made of plastic with no sharp edges on the jaws that would cut the hose.
Try crimping it down ahead of the accumulator first, then back at the tank to see if anything changes.

Most of the time it is just popping, but sometimes when it is hot it will get where it does not run well at all. The cure I have found when this happens is to burp the fuel line going into the fuel rail, almost like there is too much pressure. When it is trying to run before burping it, the fuel pressure gauge is jumping up and down. This does not happen very often.

To my mind, a good indicator that something is indeed amiss with your fuel delivery system. It should be steady and strong. No air should be able to be introduced into the system at any point I would not think. Any air in a port fuel injection system would end up leaning out the mix, and at the very least would result in a cough now and then. Or if consistent enough, the lean popping you're experiencing.

I can get some pictures or part numbers if that helps in this mystery!

Yes please!

Paul
 
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Killer Frogs

Killer Frogs

Full Member
Joined
Nov 5, 2007
Messages
317
Loc.
Amarillo, TX
Here are some pics. My thought in adding the T was the return fuel was getting chocked in the small return lines. Basically that the return fuel was not getting out fast enough.

I did clean out the first fuel filter when I put the accumulator back in.
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25e8cd6ebeeef7395201054786d16d38.jpg
7f96f881b2e0ef522f3fe15b1869b3e2.jpg
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fcf2897bea010fe5696e81c0001e2930.jpg
3c592dc45a65239e4ddc1b47fb83e6cb.jpg
b2b6131530d88afbe06f92292edcf65d.jpg
6eec98d872d3d0f4f4b0a54560ec725d.jpg


Sent from my Pixel 2 using Tapatalk
 

DirtDonk

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I'll check out the pics in a minute, but in the meantime I actually fired up the computer just to mention the fuel pressure regulator.
What pressure are you seeing on the gauge normally? And even when it's running well, do you see the gauge oscillating?
What size injectors are you running? Stock Explorer stuff all around other than that fuel rail? What is the fuel rail out of, and is the pressure regulator from an Explorer or something else?

Paul
 
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Killer Frogs

Killer Frogs

Full Member
Joined
Nov 5, 2007
Messages
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Loc.
Amarillo, TX
Paul, there is a thread I started and you commented on a few years ago where there was some thought. http://classicbroncos.com/forums/showthread.php?t=270617&referrerid=19837

I have an adjustable fuel regulator. I have run the pressure set at 46 and 65 and it does not change things. The fuel pressure gauge does not move when running well. The injectors are the stock Explorer injectors, everything else is stock Explorer. I think the rail is out of a Mustang. This is the pressure regulator Professional Products Powerflow Fuel Pressure Regulators 10679, from Summit part # PFS-10679.

Thanks
 

surfer-b

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Sep 7, 2006
Messages
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Do you have a stock Bronco fuel tank, how is the fuel being pulled from the tank, are you using the stock Bronco fuel/sending unit.
Have you tried bypassing the accumulator, as long as there is plenty of fuel in the tank you can run without it just to make sure the accumulator is not the problem. Nevermind on the accumulator, I see where you have tried this already
 

surfer-b

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What are the long term fuel trims reading, if reading above 12~15 at idle but go down when revving motor I would start looking towards a vacuum leak
 

PaveBronco

Sr. Member
Joined
Oct 30, 2012
Messages
912
I've nothing but A$$ pain with those glass filters, one because they can break if a rock or something hits it, and also because (on mine several times) the internal threaded ring that holds the filter screen would back off and cover the holes on the output side. I also wonder it this sucking air into your system. maybe throw a different filter there and see..unless you did this already.
 
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Killer Frogs

Killer Frogs

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Nov 5, 2007
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Loc.
Amarillo, TX
I was out of town over the weekend. It has the 23 gallon tank from Toms. I'm going to try a different fuel filter, getting rid of the glass one. With the changes I've tried the only things that are the same are the tank, glass filter, and high pressure pump. Cheaper to try a different filter than pump!

surfer-b- not sure what you mean with
What are the long term fuel trims reading,

As far as vacuum leak, Jason at BC Bronc felt the pops were fuel related. He had them fixed, for a brief period of time.
 
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Killer Frogs

Killer Frogs

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Nov 5, 2007
Messages
317
Loc.
Amarillo, TX
I THINK IT IS FIXED! ;D:D;D

I replaced the glass filter and the filter on the low pressure with one filter, the stock one for the Bronco. From Autozone it is Duralast FF2202DL.

I think the problem was air in the fuel filter. Today when doing some highway driving the fuel delivery was sluggish, I couldn't drive much over 45. I opened the fuel line before the fuel rail and there was a lot of air in the fuel that came out. Tonight I took it for a quick spin after installing the new filter and no pop! It also seemed more responsive. I'll drive it a little more tomorrow and see how it goes. Thanks for help!
 

PaveBronco

Sr. Member
Joined
Oct 30, 2012
Messages
912
Good news, we hope. Like I said before, I went through the same issues, its frustrating.
Keep us posted on the fix. I got my old set up you can have it this doesn't work. Carter low and high pressure pumps.
 
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Killer Frogs

Killer Frogs

Full Member
Joined
Nov 5, 2007
Messages
317
Loc.
Amarillo, TX
Good news, we hope. Like I said before, I went through the same issues, its frustrating.
Keep us posted on the fix. I got my old set up you can have it this doesn't work. Carter low and high pressure pumps.
It doesn't work, maybe even worse. PaveBronco, what setup are you running? What is the high pressure pump you are using?

Thanks

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surfer-b

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I was out of town over the weekend. It has the 23 gallon tank from Toms. I'm going to try a different fuel filter, getting rid of the glass one. With the changes I've tried the only things that are the same are the tank, glass filter, and high pressure pump. Cheaper to try a different filter than pump!

surfer-b- not sure what you mean with

As far as vacuum leak, Jason at BC Bronc felt the pops were fuel related. He had them fixed, for a brief period of time.

The fuel trims are where the PCM is adjusting the fuel/air ratio, it tries to keep it at 14.7 parts air to 1 part fuel. When reading the long term fuel trim, lets say bank 1 is 15 and bank 2 is 16 then you know the problem is gonna be common to both and if you accelerate, step on the gas pedal, and the fuel trim levels go down to say ~5/6 then you have vacuum leak, now if the trim levels go even higher, say 20 when the accelerator is pressed then its a fuel starve problem and not a vacuum leak.
I just trying to help diagnose the problem so you are not throwing parts at it
 

PaveBronco

Sr. Member
Joined
Oct 30, 2012
Messages
912
My setup was carter P4070 then the BC accumulator which I used a shorter filter, then P74028 high pressure. that pump was noisy. swapped to a BOSCH 69100 much quieter. but I still had fuel feed issues, I think now that it could have been the Russell 644113 Fuel Adapter Fittings sucking air. I ditched the whole setup for a Sherman tank with the in tank pump. Needed the extra capacity.
 
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