Help me troubleshoot a suspected fuel system problem

[CityHick]

Alright guys.. Yesterday was the first chance I'd had to get my rig out on a long trip since converting to EFI. I wanted to see how it would perform at 6000+ feet for a better sense of confidence before hitting the 'con in a few weeks. I am very glad I did this as I exposed some problems that would have sucked to hit on the trail.

The day started out great. The rig was running like an absolute champ and it was pulling long grades stronger than it ever did before. I was smiling ear to ear.

As you all know though, yesterday (Saturday 6/8) was HOT. I headed up Highway 4 and got up to around 6500 or so feet in elevation and noticed a couple of slight hesitations in acceleration. I considered it a fluke, it self corrected and so I proceeded. The rig started running very rough so I pulled over and it promptly died. Tried to restart it and it would run (roughly) and it would not respond to throttle. It was doing a little backfiring and acting like the timing was way off. I swapped out the TFI module on the side of the road and it drove awesome again for a while. It started hiccuping again 20-30 minutes later so I stopped and pulled codes. NO codes registered, no CEL indicator.

I did notice however that the inline fuel pump (Airtex model recommended by Spaceburger and others) was howling pretty loud when the engine was running rough. Cycling the key a few times would quiet it down and I could hear that it had regained prime.

SO I swapped on my spare inline fuel pump. Same thing - ran great for a while then the same crappy running conditions repeated.

Engine operating temperature never exceeded 185 all day with ambient air temps ranging from 95-105. It's never acted like this in the few hundred miles I've put on it with EFI, but I've never driven it that far in that kind of heat before.

Fuel pumps (both of them) would get pretty hot to the touch, hotter than other under-vehicle parts. My fuel pump is mounted to the inside of the frame rail opposite the muffler (offset a little so not directly across from it).

So - It seems pretty clear that with the heat I was sucking air, letting the system cool down and reprime resulted in better running temporarily.

This all has me thinking its time to (at minimum) add some strategic heat shielding around the fuel pump and maybe even directly on the muffler like OEMs do it. Possibly shielding my fuel lines as well.

I am running out of time to go about this in trial and error mode if I am to run the 'con so I am looking for some expert opinions here. I know I can't be the first to experience this kind of problem.

I am actually strongly considering going to an in-tank pump, either modifying my existing tank or buying a new tank for this purpose. I am not thrilled with that because if it fails on the trail I'm sunk unlike an inline pump that can be swapped out quickly.. but I cannot wheel my rig the way its acting now.

I have not driven it since I got it home late last night. This story has other insanity with it not related to my Bronco... so I'll stop it here.

[tim]

Re: Help me troubleshoot a suspected fuel system problem

To start out simple, I'd check for vacuum build-up in the gas tank that may be preventing fuel from being pumped from the tank. Any chance you cracked the gas cap during these events?

I'd also check all spark plugs and read for any specific issues. I recently had the #7 plug develop a condition (insulator glazing) that would cause a miss, sometimes pretty bad, but it didn't through a code.

Here's what i used for reference:

[earlybronco72]

Re: Help me troubleshoot a suspected fuel system problem

Only thing I have, since I'm a carb guy, is check your return line. I have wheeled with multiple people that have had weird things going on with thier Efi and it had been there return lines more than not.

[tim]

Re: Help me troubleshoot a suspected fuel system problem

Also, understanding that you have 2 fuels pumps, I assume you have a low pressure/high volume form the tank and into the high pressure for EFI. do you have an accumulator before the HP pump?

and forth, check your fuel filter(s) as well.

[tim]

Re: Help me troubleshoot a suspected fuel system problem

#5, do you have dual tanks and could you be sucking air from the selector valve?

[daves]

Re: Help me troubleshoot a suspected fuel system problem

Do you have an accumulator?
I switch to one pump, I had two but had to many problems with it.
I wrapped my fuel lines under the hood with this http://m.summitracing.com/parts/the-14015

[CityHick]

Re: Help me troubleshoot a suspected fuel system problem

Wow quick responses, thanks guys, this site rocks!

Spark plugs are brand new as of a couple of weeks ago. Old plugs looked fine with a few hundred EFI miles on them (and previously 6000-ish carb'd miles) but it would not hurt to check. All were approximately the same color and condition but I can certainly check the new ones too.

To clarify - I only run one fuel pump, a high-pressure Airtex E8248 which is designed to both pull from the tank and pressurize the lines. No accumulator, no low pressure pump to feed it. Spaceburger and others run this pump on its own with better results than this.

Return line seems fine, fuel is definitely making the full loop when I run the pump though yesterday I did not confirm this while on the side of the road.

Single tank, no aux, no selector valves.

Inline fuel filter is brand new, appears to be clean and flow freely.

Wrapping the fuel lines with that stuff looks like a good idea in general, not sure if that is where my issue is but thanks for the link.

[PDXBronco]

Re: Help me troubleshoot a suspected fuel system problem

Mine is running like $hit too, very similar issues. No codes either. I tried a few things like tfi, comp, tps, MAF, but to no avail. I am going back to basics and starting with a tune up then more sensors. Luckily I have a full set of replacements on the shelf. Interested to see what you find.

[CityHick]

Re: Help me troubleshoot a suspected fuel system problem

That sucks Josh! Misery loves company though - I am disappointed but not defeated, when it was running well, it was bad ass! It just did not stay that way. My real constraint right now is that I have very limited time during the weeknights and lots of conflicting weekend plans between now and the 'con run. I will find the time, but really want to make another trek once I make a few more changes. Keep the ideas coming guys. I'll try and do some more advanced diagnostics in the coming days.

This is an all OEM setup... the same setup that ran hundreds of thousands of Fords for many many years. I can't be too far away from "new car reliability" here... just need to get it dialed.

[1968u15]

Re: Help me troubleshoot a suspected fuel system problem

I think Tim's got the answer. Restricted fuel pickup from one cause or another. The pump uses fuel to cool itself. Low fuel level and no baffling in the tank, too small pick up hose, pump mounted too high in relation to the tank, poor venting, come to mind first. Best of Luck, David

[blwngsket]

Re: Help me troubleshoot a suspected fuel system problem

I run 2 pumps. Low pres at the tank. Hi pres in the engine bay after the accumulator. All of my fuel system runs down the D side of the rig. Exhaust down the pass side keeping the heat away. Seems to work very well.
Checking the gas cap is a good idea. Tank vaccum will shut you down fast. Had similar issues with my chopper.
Happy hunting. I'm sure you'll figure it out.

[71BRONCO71]

Re: Help me troubleshoot a suspected fuel system problem

Keep in mind it was super hot air, and high elevation. The air was thinner then its ever been.

Fuel accumulator, heat shield or wrap the fuel lines sound like the fix.

Is your fuel line running from the tank to the motor hard line or soft?

[Bradical69]

Re: Help me troubleshoot a suspected fuel system problem

It may be a fuel pump issue (I've ran one pump and 2 pumps w/accumulator just fine) but it kinda sounds like a problem tiewire had last year, would run fine then bad missfire and hardly ran. No codes were thrown but we (he) figured out that his mass air flow sensor was bad. When he got a new one it ran just fine. I still don't know why it didn't throw a code.

[Broncrick]

Re: Help me troubleshoot a suspected fuel system problem

I want to say fuel related also.... unless the bap is bad/intermittent

Why only one pump? Ford designed it with two, which is what I run, LP at tank, HP on fender well. I did have a hot HP pump once at Miller Lake, after a weekend going through the trail, nothing since.

Do you have any rubber line before the pump that could be collapsing during suction?

I will think about this some more, hmmm

[CityHick]

Re: Help me troubleshoot a suspected fuel system problem

Tank vacuum was a concern of mine. I cracked the gas cap open and did not hear air rushing past. I have a vent running to a charcoal canister from the tank. At one point I pulled the vent line off of the canister just to eliminate that as a possibility, it made no difference.

BAP sensor is brand new (as are all of my efi-related sensors... not to say you can't get bad parts out of the box).

The Airtex pump that I run is supposed to be able to do both functions - pulling from the tank and pressurizing forward to the rails. I don't love the idea of two pumps (more parts to fail) but that may be something I could try too.

Fuel line is mostly efi-rated AN hose, reinforced and it should not be collapsing. There is a little hard line but as memory serves that's actually part of the return. You got me thinking though... its possible that the hose right off of the tank might not be EFI hose... hmm.

I am going to do a little investigating this evening if I get home early enough, scan for codes again, etc. Little road testing too, just to see if its still acting up or if the problem really is heat/elevation specific.

It bothers me that the rig ran so well and gave no failure indications at all until around lunch time when I'd been driving for several hours... though fuel system issues brought upon by heat and/or elevation can be tricky.

I love a good puzzle... to be continued!