Explorer EFI - random acceleration problems - SOLVED

[Amitchla]

Hi guys,

The Bronco has been having intermittent power loss under load lately, and I'm trying to figure out what it is. My current guess is that it may be associated with the inline fuel pumps that are being used.

Basically, the truck will randomly become gutless. It most often has happened at highway speed. I'll be cruising along at 60-70mph, and the engine will suddenly lose power. It won't shut off - I can still rev the engine - but I won't be able to hold steady speed. So far, after pulling over, restarting the engine, and revving it for a couple of minutes, it will perk back up and drive off. It has happened more frequently lately, which has had me working to figure out what the problem is, prior to needing a long tow home.

The truck has the Explorer EFI set up, and has dual inline fuel pumps and a 23gal tank. The pump that's closer to the fuel tank (probably 18-24 inches away) is a Carter 60430 (low pressure), and then there's one that's mounted in the engine bay that is high pressure - likely an Airtek 8228 or the like, though I haven't unwrapped it to find any numbers.

I have no way of knowing exactly how old these are.

The pressure gauge sits around 40psi when idling. I haven't been able to hop out and check the pressure during one of these bouts, as of yet.

1. Is this the appropriate set up for dual inline pumps, as far as distance?

2. I do have an extra low pressure pump that came with the truck. Is it worth swapping this in, to see if it fixes the problem?

3. Does this sound like a fuel problem?

4. Is there a way to tell if either of the pumps is going bad?

5. Any other possible solutions you can think of?

TIA - as always!

 

[bax]

It does sound fuel related. Do you ever get a backfire during this? A lean backfire at high speeds would also indicate fuel issue. External pumps on broncos can be a problem due to mounting locations. Ideally you want your pump lower than your tank. Thats kinda hard because of the location of the tank and the best mounting positions. I run a large frame mounted filter. I feel it holds enough fuel to act like an accumulator. A slave pump should always be able to keep it full. I also used run my high pressure pump right in front of this filter. Slave- filter - high pressure. Pumps don't pull fuel very well. Thats one of the reasons for in tank pumps. I also increased my line size to 3/8''. The Carter pumps can get trash in them. It is possible to clean them. I would also look into that.

 

[Amitchla]

Thanks Bax. Yes - it does indeed backfire at speed when it loses power.

The low pressure pump (Carter) is the type that comes with the fuel filter that's affixed between the pump and the tank, so as to filter the fuel prior to the pump itself. This one is frame mounted.

The second, high pressure pump is located in the engine bay, between the charcoal cannister and the engine itself.

I was planning to swap out the filter, since it's easy and cheap. Is there any way to check the pumps without just wholesale swapping them out? From what I've read online, it sounds like you just listen for excessive noise, diagnose symptoms, and then replace as necessary, but I just wanted to make sure before I start throwing more money at the thing (as usual, lol).

 

[bax]

I would move my high pressure pump down next to the other pump. It will put it lower. They push better than they pull

 

[Amitchla]

That makes sense!

Will the high pressure pump be able to push through the charcoal cannister? I don't really understand those mechanics.

 

[bax]

Canister is for fuel vapor from the vent of the tank. I sure hope you are not running your presurised fuel thru the canister?

 

[Timmy390]

Works like a champ

Tim

 

[Amitchla]

@bax i would say yes - it looks like that’s how it was plumbed by the PO. It sounds like I should do some rerouting?

See pic.

Canister is for fuel vapor from the vent of the tank. I sure hope you are not running your presurised fuel thru the canister?

 

[bax]

The picture helps a lot. Not what I was thinking. So you have a screw in style fuel filter that is fed by a frame mounted low pressure fuel pump. The pump fills the filter and feeds the HP pump. Your HP pump is mounted on your inner fender well thus making a very short run to your motor. Thats what I Get from the picture. Correct? Now I think I would do this differently.

 

[bax]

Honestly when you said canister, I thought you were running fuel into your charcoal canister. So glad you are not doing that. Without a HP pump in your tank, you use a slave / low pressure pump to keep the HP pump stay primed. But the HP pump can pump a greater volume of fuel if you can keep it primed. With the short HP fuel line you are currently running you have very little pressure recovery time if the Low pressure pump can't keep the canister full. I would change things around some if it were me. First off I dont like the canister filter mounted to the core support. It is unprotected if you get crunched in the drivers front corner. Could be bad. I would take both pumps to the rear inside frame rail and mount them close to the tank . LP first. then your canister / screw on filter right to your HP pump. Your LP pump will keep the filter full and your Hp will have the added line volume due to the longer length of high pressure fuel line to keep your engine from running out of fuel.. I run this type of set up on the dark blue bronco you see in the avatar. Works good. When I re do that bronco I will change the tank and put an in tank pump in it. I have a different bronco that has a Wild Horses tank with a pump inside it. I have zero issues with the motor getting enough fuel.

 

[Amitchla]

Ok, got it! To be honest, I thought that this fuel filter was a charcoal cannister I’m definitely still learning about late model engines and their various newfangled parts.

Understood on desirable locations for the pumps and filter. I’ll have to do some fiddling to see if I can move everything around.

I replaced the low pressure pump today (there was an extra in the off-roading toolbox), and the issue remains, so that must not have been the problem.

The high pressure pump is making some noise, but nothing too crazy.

The problem currently seems to persist for the first 30sec-1min of driving under load, and then the truck runs fine. I haven’t driven it on the highway to test if it randomly does this at speed… but i assume nothing has changed.

 

[bax]

Your IAC may need cleaning. That could help the cold running issues.

 

[Amitchla]

Ok - further update on this. I went to take the truck out to the desert today, and couldn't get it through the pass in the mountains. Under load, and at WOT, the truck backfires and loses power completely.

If I *barely* press the gas, I can rev it through the full RPM range, but any further than that and it will just lug and pop and sputter; basically, it's gutless, which is embarrassing for a 347

I went ahead and ordered a new screw in filter (which Amazon has now lost twice, dammit), and a new high pressure inline fuel pump from WH. Once that's here, I'll shift it's location to closer to the fuel tank, as Bax suggested above.

I also ran the codes when I got home (which I always forget that I can do on this truck - I'm so used to pre-computer motors), and got the following:

22
81
82
84
85

I believe, from reading a bit, that all 81 - 85 all relate to emissions, which the truck is not set up for.

**EDIT** is the Idle Air Solenoid the same as the IAC? If so, this would indicate that the IAC should be changed too, right?

22 indicates the MAP/MAF, which is a Pro M Racing with some hand-scratched model numbers on the sensor itself. I dug around and verified that the computer it's paired with is the A9L from a fox body Mustang.

I emailed Pro M to see what they suggest. I assume that, since this is a performance part, I shouldn't just replace it with something from the 'Zone, right?

Stay tuned - I'll continue to update.

 

[Amitchla]

After poking around on the Pro M website, it looks like the AFM is a 75mm made for 24lb injectors. Hopefully Pro M can give me some guidance on testing the resistance on the current AFM to see if it indeed needs to be replaced.

I cleaned the IAC last night as well, but it wasn’t very dirty. I’ll be reinstalling today and rerunning codes to see if anything changes.

 

[onpier55]

Check the diode fuse. Mine was not tight and would do the same thing. Made a better connection and it quit dying after hitting a bump. Good luck.

 

[Amitchla]

Just to close the loop for anyone who has similar problems in the future - the fixer for me was cleaning the overly dirty MAF.

I was having the GF come down to rev to WOT while I watched the fuel gauge. While giving her a "demo of what WOT is," I revved the engine without the air filter, and the problem *semi* went away, which made me wonder further about the MAF. After taking it out, the front side of both wires were covered in carbon/gunk. I took acetone and a q-tip and *very lightly* rubbed both wires clean.

After this, I took the truck out for a spin, and it felt as powerful as ever! PROBLEM SOLVED.

 

[bax]

Oh yeah cleaning the MAF may help.

 

[ntsqd]

Just for future ref there is a product made specifically for cleaning MAF's.

Looking at the pic above I'm wondering if that is either a copy of or the BCB by-passing fuel filter/accumulator assembly? If the line that appears to be T'd is part of the return line then I'm pretty sure of this.
Look here: https://bcbroncos.com/shop/fuel/fue...lter-42737-qt-short-version-for-early-bronco/ See the similarity?