Hi,
I have a 1986 Bronco II with a major fuel issue.

On start up it runs real smooth, no problems. After a bit of driving vehicle studders and stalls like it's out of gas. Let it cool off for a bit, starts right back up, then does it again a few miles down the road again.

First diagnosis: hooked it up to computer, only error was code 11/33 EGR valve.
REPLACED IT

Problems still happening.

Second diagnosis: Bought a fuel pressure gauge. Ran about 35 psi at start up till it got warm, then dropped from 35 psi to 10 psi then died.
REPLACED HIGH PRESSURE FUEL PUMP

Problems still happening.

Third diagnosis: Read many threads about the Ignition Control Module. Thought maybe that was it.
REPLACED IT

Problems still happening.

Now I went ahead and purchased both fuel filters, rear booster pump, and a complete tune-up kit. I would like to return these items if they are not necessary, so I need some advice on what to do next? I've already purchased the high pressure fuel pump, module, EGR valve, and now have extras in perfect working order!

How do I test the fuel pump relay?
How do I test the booster without pulling it?
Any particular vacuum hoses I might have missed that would cause this?

Being that the regulator is after the fuel rail where you test the pressure, I figured this wasn't the problem. Am I right?

What am I missing?????

Thanks,
Matt

 

Hi and welcome to FTE! Thread moved to Bronco II forum.

Read this for some info that will help you around the site: https://www.ford-trucks.com/forums/s...92&postcount=2

-Matt

 

That sure sounds like fuel filters to me. I would put them in! If you have two tanks, are the symptoms identical on both tanks? (Indicates problems with in tank pump). If you are located near southern OR, we have a parts Bronco II dirt cheap with two good tanks, lines, and working pumps for under $100 if you need it. 5414764084 phone.

 

"Being that the regulator is after the fuel rail where you test the pressure, I figured this wasn't the problem. Am I right?" -- Not necessarily, the FPR is a mechanical back pressure regulator. However, most failure modes of the FPR are not going to be intermittent like that.

Rather than replacing a bunch of stuff, I would start by diagnosing the known bad parameter: low fuel pressure.
When the fuel pressure is low, can you hear the pumps running? This should be pretty quick and easy, especially if you have a stethoscope or equivalent. If you can hear the pumps running, can you hear fuel running back into the fuel tank? If you can't hear the pumps running, then verify that the pumps are getting power.
As you test the pumps for power, you will also be testing the relay. As an aid, they put a fuel pump test lead in the self-test connector (short end of trapezoid if memory serves) that allows you to ground the relay for testing. Turn the key on and ground the test lead. Then locate the wire that goes back to the pumps. If you have +12V at this wire (referenced to ground), then the relay is working, and the fault is farther down the circuit. If you don't have +12V, then the fault is in the relay or upstream of the relay (fuse or other wire).
As with any electrical diagnosis, if you don't have a wiring diagram, start by getting a diagram so you can see how the circuit is supposed to look.

 

Okay, after much discussions, after listening to everyone's ideas, opinions, etc. I decided to do some testing.

Since I know that after about ten minutes of idling, I lose most of my fuel pressure and it dies. I know that it has to be something with fuel. And since this only happens after it warms up, it shouldn't be the relay. They either work or they don't. The regulator from what everyone tells me just boosts the pressure for the injectors. To test if it's working, pull the vacuum hose off, and it should go up 5 plus psi. It did. So I moved down to the fuel filter. Replaced 3000 miles ago. HMMM..... on to the next. High pressure fuel pump. REPLACED. Ok. Further back is the old inline canister that a round type of fuel filter goes in. Filter was not even in there. Somebody wrote "no filter" on the side of it. Inside was nice and clean. Ok. So I turned on the car with both fuel lines unhooked from the canister, and no fuel came out.
HMMMMMM................ Could this be my culprit? The rear fuel booster? If this doesn't work, could the high pressure fuel pump be shutting down?
First thing this morning I turned on the Bronco II and I could easily hear the front fuel pump. The other I thought I could hear. After awhile, when it would start dying, the front fuel pump made some weird sounds like it wasn't getting gas. After I unhooked the two gas lines, turned the key on, and no gas would come out.
So, I dropped the gas tank. That was fun.
Cleaned up the tank, removed sender unit. Found out that buying a new booster pump doesn't mean a new drop-in part. you have to rebuild the entire sender unit booster contraption. I had to go back and get the new filter, as the old one tore off.
Anyways,
I put the "new" setup back into the gas tank. I propped the gas tank up enough to hook up lines and power. Turned the key on, and heard the little pump purring away. I had forgotten about the two lines I had unhooked from the canister, and saw gas coming out of them. You might ask, so was this the problem???

I'll let everyone know tomorrow, as we had to end early for poker night. Priorities...

Gas line clips, vacuum hoses, re-attach gas tank, filler hose, gas tank straps, skid plate, bumper Plastic cover. Then test drive!!

Matt
1986 Bronco II Automatic-This is my nephew's!!!
1987 Bronco II 4-speed
1993 Bronco Eddie Baur

 

Problem fixed!!

Rear fuel pump booster was faulty!

 

glad to hear you got it going!