EFI stalls with bumps

[bdawson]

My engine seems to stall with every significant bump as if its not getting any fuel. The suspension is very stiff and have already ordered a Duff replacement but just doesn't seem like EFI should stall with bumps.
I have a 5.0 mustang engine with frame mount pump. Also I am not sure if its being vented properly. When removing the gas cap I get a significant rush of air. The garage smells of gas strongly in the morning but can't seem to find a leak.
Also, notice the speed sensor isn't hooked up to anything. The fuel gauge doesn't work but was told it was the fuel sending unit and it came with the replacement part for that.

Here are some pics of the setup, not sure if the cap is vented. Had the bronco about a month and half so still learning it all. Any help would be greatly appreciated.

 

[pcf_mark]

I think I would start with the fuel filter / distribution point / return line mounted near the power brakes. You fuel in and fuel out are on the top side. If you get any air in that (like from the pump or fuel tank being low) the air will rise to the top and give your engine air not fuel. I would flip that over as a test.

You can count a fuel pressure gauge on the rail and cell phone and get some video of the fuel pressure changes you would know it was fuel.

 

[patterdale]

I think I would start with the fuel filter / distribution point / return line mounted near the power brakes. You fuel in and fuel out are on the top side. If you get any air in that (like from the pump or fuel tank being low) the air will rise to the top and give your engine air not fuel. I would flip that over as a test.

You can count a fuel pressure gauge on the rail and cell phone and get some video of the fuel pressure changes you would know it was fuel.

If you have an inertia switch that could be the problem.

 

[Viperwolf1]

Sounds like an intermittent electrical problem. I see cheesy wiring at the pump.

 

[904Bronco]

I see a clear plastic fuel hose from the tank to the pump that needs to be replaced with real EFI fuel hose!

Also it looks like a standard fuel filter designed for low fuel pressure? Should be upgraded to an EFI type filter/ with EFI hose clamps...

Lots of little things need looked over and upgraded.

 

[crawler73]

The fuel filter is before the pump so it shouldn't make a difference if it's low or high pressure or am I mistaken?

 

[904Bronco]

For in-tank pump longevity, there should be some kind of inlet filter (a sock) and then another filter prior to the injectors.

For an external pump, assuming he is using a factory sending unit, a filter prior to the pump would be prudent.

So in looking at his pictures more closely... This is probably a low pressure pump to fill his Fram filter/reservoir and I now see that there is a second HP pump.

I stand corrected...

While this fuel supply system has been successfully used by many, I find it too busy. There are many parts that can fail and give a fuel delivery problem. Junk in the tank, sock/pre-filter that needs changed, tired pusher pump, pusher pump not rated to draw unless it is close to the tank, wiring, etc...

All that and Todays gas formulas really does a number on our fuel systems.

Change that clear hose for real fuel line, check wiring, change filters if unsure of age, check fuel pressure on the low and high sides...

 

[DirtDonk]

What year is your Bronco and what year was the engine donor?
More curious than anything else, but that info might help with some things.

If a '70 or early then your gas cap is of the early vented type, which lets fumes out too. That might be your smell issue, but of course it could be many other things too. You'll have to hunt that down.
If it's a mid-'70 or later, does it still have the evap/charcoal canister system connected? If so, the plastic tank behind the driver's shoulder behind a panel could be leaking. Very common to split a seam over the last 40-ish years or so.

If you have air rushing in after the truck has been running, first try driving around without the cap to see if your stalling problem goes away. If so, you need to either replace the cap or drill a hole in it.
Yes, it will smell some more if you drill the hole, but at least it will run better.
Seems like a replacement cap would be best, but check things first.

ON a side note, where does your PCV clean-air return hose connect? That's the one connected to the oil filler tube just under the cap. It should be connected to the intake tubing between the MAF sensor and the throttle body. But should not be attached to a full intake vacuum port.

Good luck.

Paul

 

[DirtDonk]

Forgot what I was going to ask first...
Is it possible that the hoses are incorrectly connected to the reservoir there under the hood? Isn't one port for fuel-in, which would be terminated higher up in the canister? Then the pickup tube (fuel out to the hp pump) would be extended to the bottom of the tank.
Correct?

If it's plumbed backwards wouldn't that possibly get air in the system when it's bouncing around?
Does it die instantly the moment a bump is hit? If so, it's probably electrical anyway, but thought I'd throw out a few suggestions with regard to the fuel end of things anyway.

Paul

 

[bdawson]

Thanks for the help, I'll take a look more closely at the wiring and replace that gas line. Today it actually died on me and didn't keep going. Stopped and it restarted after about 30 seconds, went and filled it back up with gas, had about a half tank in it. Removed the gas cap to fill it and big rush of air again. Got home and removed the gas cap, huge rush of air and decent amount of gas rushed out. Think the gas cap is the solution there?

 

[bigmuddy]

Sounds like a crimped vent line at the tank.

Too, make sure that all in coming air goes through the MAF. IF you used rubber caps to block off the various left over vacuum line ports they may crack quickly and suck air. It will run like crap.

 

[Rustytruck]

What did you change since it last ran properly?

 

[riggermortis]

Just a thought, when I first set up the efi on mine I had the same frame mounted pump, mine would die intermittently also when I let the clutch out from a stop light. What I found was I didn't actually have a ground strap to the frame, had one from the battery to the block and from the battery to the body so the only thing grounding to the frame was my worn out clutch linkage once I grounded the frame never had another problem. I will also second most of the suggestions listed above.

 

[riggermortis]

I also had the rush of air out of the cap and that turned out to be a faulty venting cap.

 

[nvrstuk]

If this happens INSTANTLY when you hit a bump and it ONLY happens when you hit a bump, it's electrical . A faulty gas flow problem will occur at OTHER times also! Check all electrical connections- all.

 

[nvrstuk]

Faulty caps cause problems but not only when you hit a bump.