1986 Bronco II EB 4wd 2.9 gas - warmed up dies no run for 20+ minutes

[Tiha]

Last month the mech said he measured fuel pressure and gets 40 while running and watched it die all to less than 10

That sounds like it runs out of fuel. Am I reading that right?

I haven't dealt with the B2 much I will admit. At least not the system you have. But I had gotten to the point on the dual system pumps I was bypassing the rail pump and putting a larger single pump in the tank.
The majority of the ones I did were 460 engines. In F350s, 4 door broncos and motorhomes but it fixed the issues every time.

The Issues were odd. Usually hard starting when hot, or vapor locking basically. Went through quite a process to get to that point but when we tried it on the first one it became a standard practice for us.

 

[Tpremru]

First off, pinching off a file line isn’t a very good way to test the fuel delivery system because the volume demand is taken away and all you are testing is the hp pumps ability to produce pressure. That is not your issue.
Plus it will damage the plastic lines.
If it dropped to 10 as it was acting up, the fuel delivery is most certainly your issue.
I don’t want to be “that guy” as I’m not able to physically test your truck, but based on the ongoing story it sounds like your guy is throwing darts, “the parts till it starts” method of diagnosis.
I’m also not a fan of FS1, I tried dealing with them for the ecm for my 79 resto mod.

I would continue down the path of an intermittent issue with the low pressure pump, either voltage loss in the wiring, or a blockage within the tank.
You might look for a tech with more experience in the older systems, or is at least willing to research first.
The most important thing to know is how it is supposed to work when trying to fix something.
Hope that helps.

Thanks L\Bronco i think this does help as i think on this everyday for such a long time. This takes the words out of my mouth--->"I would continue down the path of an intermittent issue with the low pressure pump, either voltage loss in the wiring, or a blockage within the tank."

I hope the mech calls me back today and i can convince him to go this route whatever it takes!

 

[Motech]

the dual system pumps I was bypassing the rail pump and putting a larger single pump in the tank.

What a great idea! It had probably been 10 years since my last one, but I recently had to wrestle with an older Econoline dual pump setup. I'm going to totally go this route next one (which just might be that Econoline)

Did you just hang a higher output pump on the existing carrier? Or did you go with an entirely different assembly?

Any tips you could provide would be most appreciated. If you don't want to bugger up this thread, feel free to shoot me a private message.

Or maybe even start an informational threat about it?

 

[Tiha]

What a great idea! It had probably been 10 years since my last one, but I recently had to wrestle with an older Econoline dual pump setup. I'm going to totally go this route next one (which just might be that Econoline)

Did you just hang a higher output pump on the existing carrier? Or did you go with an entirely different assembly?

Any tips you could provide would be most appreciated. If you don't want to bugger up this thread, feel free to shoot me a private message.

Or maybe even start an informational threat about it?

Back in the early days (for me) we had problems and kept flow testing pumps, flow test hot, flow test cold. Seems like you put a new pump in today and next week it will fail flow test. We tried everything. FPRs, that stupid canister thing under the truck. Injectors. Nothing made a difference, but fuel flow the only thing that was always borderline.

I don't remember all the specs now, but I was thinking for the Ford 460 it was around 130 liters per hour flow. (around 30 gallons per hour) (could totally be off there)
So we were buying 155lph pumps from Summit racing, Just generic high pressure fuel pump.

At first went all out. Soldered a new pipe to the existing hanger to help support the weight of the pump.

After we did a few of them, now we just hose clamp the new pump on and leave it. Seems to be holding up just fine. We have a motorhome here that has been running 12 years now that way. They work it hard too, pulling trailers with it.

At that time you could get metal fuel line repair pieces from the help section at parts store. We used that to bypass the frame rail pump. Quick, fast, and easy.
Just plugs right in. No effort required.

Then you can see the pics below. You spend most of your time setting the depth of the new pump. After that splice the harness, then plug and play.

 

[Tiha]

Fuel line used to bypass frame rail pump.

Dorman - OE Solutions STEEL FUEL LINE REPAIR KIT. 3/8 IN. x 12 IN. DOUBLE BEAD LINE.

Not sure anymore but parts stores used to have them in the help section. Came in a pack with 1 of 5/16 and 1 of 3/8.

Which if you wanted to bypass the canister you needed both.

 

[Motech]

Awesome response @Tiha ,thank you VERY much!

 

[Tpremru]

To everyone: Thanks for your helping me assemble a plan! WE KNOW IT'S FUEL PRESSURE PROBLEM. It's been measured 3 times by different people - reminder - it drops from 40 to 10 or less when the issue of coughing and dying happens. A couple people are still asking about spark...i don't know that answer but i'm going to ask for due diligence and make mech prove spark is not lost at time of issue, (but when you try to start it, it coughs and sputters like its sparking without enough fuel) see video posted earlier.

Plan with a few mods:

1. Due diligence proving spark at time of issue.
2. Drop the tank & fully drain it.
3. Fully inspect the current fuel sock and the inside of tank for any debris and remove metal flapper if possible.
4. Prove that fuel line and return line and connectors have no problems.
5. if possible, run Lpump while submersed for flow check for 20 minutes (this length of time coincides with the Hpump sound-this would check the wire and the Lpump itself)
6. (Good time to do this)-> Inspect float because full tank registered not quite 7/8. Bend arm to adjust instrument fuel guage a.ccuracy
7. Inspect the fuel filter in the canister.
8. Add hot/grnd test lead to fuel send plug.
9. Reinstall fuel tank.
10. 
    
11. Add test leads to Hpump
12. 
    
13. Get voltage and amperage levels Lpump & Hpump while running good.
14. Get voltage and amperage levels when issue occurs (this will be the trick and crucial part if issue is not resolved in #1)

Any problems found at any step may provide the resolve and make remaining steps unnecessary.

Now i am wondering how many hours is this gonna take $$$$? Any idea?

Also as i mentioned a couple days ago:
It seems this 1986-1988 was a bad idea using 2 fuel pumps. 1989-90 uses one. This makes me ask the question "If we determine inside of my fuel tank is rusty etc and need a new one....i wonder if i can fit a 1989 or 90 fuel tank that only uses 1 fuel pump and upgrade to that type of system? The ECM shouldn't care that it only has 1 wire to send anyhow, and there is a FP regulator?

 

[johnnyreb]

To everyone: Thanks for your helping me assemble a plan! WE KNOW IT'S FUEL PRESSURE PROBLEM. It's been measured 3 times by different people - reminder - it drops from 40 to 10 or less when the issue of coughing and dying happens. A couple people are still asking about spark...i don't know that answer but i'm going to ask for due diligence and make mech prove spark is not lost at time of issue, (but when you try to start it, it coughs and sputters like its sparking without enough fuel) see video posted earlier.

Plan with a few mods:

1. Due diligence proving spark at time of issue.
2. Drop the tank & fully drain it.
3. Fully inspect the current fuel sock and the inside of tank for any debris and remove metal flapper if possible.
4. Prove that fuel line and return line and connectors have no problems.
5. if possible, run Lpump while submersed for flow check for 20 minutes (this length of time coincides with the Hpump sound-this would check the wire and the Lpump itself)
6. (Good time to do this)-> Inspect float because full tank registered not quite 7/8. Bend arm to adjust instrument fuel guage a.ccuracy
7. Inspect the fuel filter in the canister.
8. Add hot/grnd test lead to fuel send plug.
9. Reinstall fuel tank.
10. 
    
11. Add test leads to Hpump
12. 
    
13. Get voltage and amperage levels Lpump & Hpump while running good.
14. Get voltage and amperage levels when issue occurs (this will be the trick and crucial part if issue is not resolved in #1)

Any problems found at any step may provide the resolve and make remaining steps unnecessary.

Now i am wondering how many hours is this gonna take $$$$? Any idea?

Also as i mentioned a couple days ago:
It seems this 1986-1988 was a bad idea using 2 fuel pumps. 1989-90 uses one. This makes me ask the question "If we determine inside of my fuel tank is rusty etc and need a new one....i wonder if i can fit a 1989 or 90 fuel tank that only uses 1 fuel pump and upgrade to that type of system? The ECM shouldn't care that it only has 1 wire to send anyhow, and there is a FP regulator?

If Ford changed it in 89 . Seems like they were having problems with the 2 pump also. I,d go with one.

 

[Tpremru]

This sounds just like my issue....https://www.ford-trucks.com/forums/512439-bronco-ii-fuel-issues.html

 

[Tiha]

This sounds just like my issue....https://www.ford-trucks.com/forums/512439-bronco-ii-fuel-issues.html

Sure does, so he is saying the intank pump is bad.

 

[Tpremru]

Sure does, so he is saying the intank pump is bad.

That's right the Lift pump...this is the closest described issue to my issue that i have found.

The past couple of days i was thinking maybe because i have spent so many $,$$$ on this and a couple of people have allegedly checked many things, in my mind i'm going to cut to the chase do an easier test before going to the plan i laid out earlier - i think i can buy same gauge wire and do a temp hot & grnd wire replacement from under the master cycinder to the Lpump. If that does not make a difference (gut feeling it really is the grnd wire) then i remove the temp hot wire and connect the temp grnd to see which or both make a difference.- Even though i have looked and taken pics of harness on the frame, I don't know how many connection points there are for the grnd wire and where are they (i looked took pics but not much help)? I am also sure that i want to get a wire from the plug not splice into the wire from the plug and i know i can't unplug the Lpump without dropping the tank.

 

[Tpremru]

Thanks L\Bronco i think this does help as i think on this everyday for such a long time. This takes the words out of my mouth--->"I would continue down the path of an intermittent issue with the low pressure pump, either voltage loss in the wiring, or a blockage within the tank."

I hope the mech calls me back today and i can convince him to go this route whatever it takes!

Just you know...thanks for all your input! A few minutes ago I talked to the Mechanic and i can book some time on week of Jan 30th. SO I WILL POST back here later than that date to let you know if we find nothing or it's fixed! After talking it over the first thing is still:

"I would continue down the path of an intermittent issue with the low pressure pump, either voltage loss in the wiring, or a blockage within the tank."

 

[Tpremru]

An important update here....today i drove for 60 mintes about 25 miles ran fine even into passing gear, pedal down etc. then idled in the driveway for 27 minutes and it conched out. I could hear the Hpump engage when key on so:

1. I disconnected the Hpump and left only the Lpump connected, grounded pin#6 on OBD and climbed under tank even with a stephoscope i could hear nothing.
2. I toucked the top of fuel send unit and could feel no vibes, touched all 4 wires and none were hot.
3. I Touched the ECM and both Relay's and they were as about as warm as expected.
4. The 3 wires for pumps under master cylinder were not hot.
5. When i reconnected the Hpump and did the pin#6 grnd test - there was air like sounds coming from the fuel tank - like maybe the Hpump lost it's prime and was sucking trying to get primed - or bubbles coming from the return line?

Cooled down 30 minutes then it would restart and seems to run fine.
I'm on the schedule for the shop to do any tank dropping testing etc the first week of February.

 

[Tiha]

So it might seem like a silly question, but can you test and get power on any of the dead wires now when it runs?

 

[Tpremru]

I can't get to the plug on the Lpump until we drop the tank. Otherwise i don't really want to pierce the wires back there. Still puzzling is that when it restarted finnally and ran ok, i shut it down and disconnected the Hpump and the Lpump still won't come on. I'm going to try the Lpump again tomorrow. I know on the 29th both pumps worked because i hooked them up seperately and recorded the sounds of each!

 

[Tpremru]

I can't get to the plug on the Lpump until we drop the tank. Otherwise i don't really want to pierce the wires back there. Still puzzling is that when it restarted finnally and ran ok, i shut it down and disconnected the Hpump and the Lpump still won't come on. I'm going to try the Lpump again tomorrow. I know on the 29th both pumps worked because i hooked them up seperately and recorded the sounds of each!

Nope the Lpump does not run today either. So bad wire or bad pump, won't know until i can it to shop to drop the tank first week of Februrary. Does anyone know where the next connection point of the ground wire that belongs to the Lpump?

 

[Motech]

Th

Does anyone know where the next connection point of the ground wire that belongs to the Lpump?

Both pumps get their ground from G200-Behind Instrument Panel, To Left Of Steering Column. Should be recognizable by a green bolt, 8mm head.

Here's your diagram:



Looks like it splices off at S305 and S304 downstream of the HP pump, and they share the same connector C118.

Splice locations:
S303-Near RH Rear Lamps Take Out
S304-Near Seatbelt Switch Take Out (Bronco II)

Connector location:
C118-LH Fender Apron

 

[Tpremru]

Both pumps get their ground from G200-Behind Instrument Panel, To Left Of Steering Column. Should be recognizable by a green bolt, 8mm head.

Looks like it splices off at S305 and S304 downstream of the HP pump, and they share the same connector C118.

Splice locations:
S303-Near RH Rear Lamps Take Out
S304-Near Seatbelt Switch Take Out (Bronco II)

Connector location:
C118-LH Fender Apron

Thank you Motech! In the next couple of days i'm going to be trying to find G200, S303, S304 and C118. I climbed underneatch yesterday and took lots of pics trying to follow the harness. I also plan to do a "guitar cord" test = grnd pin#6, climb underneath wiggle as much and wherever i can, up topside wiggle relays and connectors under driver side apron to see if Lpump will spin even for a moment. I'll report back then!

 

[Tpremru]

I also plan to do a "guitar cord" test = grnd pin#6, climb underneath wiggle as much and wherever i can, up topside wiggle relays and connectors under driver side apron to see if Lpump will spin even for a moment. I'll report back then!

More puzzling...i turned the key on make sure i can hear Hpump, i disconnect Hpump leave Lpump connected, i turn the key on and low and behold i can hear it prime up, did that 3 times. Yesterday i connected and disconnected 3 times and Lpump would not come on.

So i grnd to pin#6, turn key on and yes still the Lpump is working. I climb all over underneath moving all wires from the very Lpump pigtail all the way to past the Hpump. I moved the wires around under the master cyclinder, then the relays. The Lpump stayed running this whole time no change. I disconnected the grnd to pin#6, turned the key to on and heard the Lpump prime up. I tried to start it 3 times and it would not start just as i expected. Then i said "let's hear that pump again before i reconnect the Hpump". The Lpump is not priming so i grnd pin#6 and still no Lpump. I reconnected Hpump and started it up and it runs.

Why did the Lpump stop working when i tried 3 times to start it with only Lpump connected? I'm going to have to check if Lpump will come on again tomorrow.

 

[Tiha]

It could be an electrical issue, but back in the day they told us that a fuel pump would get hot and stop, cool down and start.
Or get hot and stick.

So a car would die, no fuel pressure, get towed home, start to test it, car starts right up as if nothing is wrong.