86 Ranger, fuel delivery problem

bossbob · Dec 28, 2017

So, I have this 86 ranger, 2.9, 5 spd. bought it for my son, it's been running fine for the most part. Tonight the fuel pumped died, or at least that is what I'm guessing. Towed it home and will start investigating tomorrow.

Here's the deal, the previous owner put a switch in to directly turn the pump on or off, and by-passed the inertia switch. I would like to figure out what or why he did this. I'm assuming the inertia switch is bad.

1. What do I test first to make sure the if the pump is good or bad.
2. Is there more than 1 pump I need to look for.
3. What questions should I have ready to answer for you tomorrow.

Once i have this figured out, what do I do to put the safety inertia switch back in order.

Thanks

Shran · Dec 29, 2017

bossbob said:
1. What do I test first to make sure the if the pump is good or bad.

If you can hear it running, it's probably good. The in-tank pump is very quiet, you may have to unplug the other one and put your ear close to the tank while someone cycles the key. If you can't hear it, it's bad, or it doesn't have power.

2. Is there more than 1 pump I need to look for.

Yes, there is one in the tank and one on the driver's side frame rail just behind the fuel filter.

I'd try to determine why the switch was added, remove it, and fix whatever caused the previous owner to add the switch.

I hate it when people do crap like that. I've seen trucks that simply needed a new relay - the owner thought it best to add another mile of wire and three more layers of complexity to a simple problem.

alwaysFlOoReD · Dec 29, 2017

One other thing to note, the fuel pumps only run for approximately 2 seconds then shut off. They do this each time the key is turned until the engine starts.

In tank pump is low pressure lift pump. Frame rail is high pressure pump.

I've found that the wires behind the boot on the high pressure pump can be loose and cause problems. I test using direct battery jumpers to the terminals on the fuel pump. Don't run it long. If tested good I cut the wire terminal ends and crimp on new female spade terminals using the correct ratcheting crimper. I almost tossed two good pumps because the wires were loose.

Buy or rent an EFI fuel pressure tester. There is a Schrader valve, looks like a tire valve, on the fuel line on top of the engine. You should be getting 40psi or close. The pressure should hold for days, if not, there is a leak. Leaks can be internal to the pump or pressure regulator so you won't see or smell gas. If you have pressure the problem is probably not fuel related.

bossbob · Dec 29, 2017

I was able to rig it back together short term.

Turns out there is a wire from the passenger side pink/black that the PO tapped into. He runs it across the fire wall into the rocker switch. Then from the fuse panel to the switch for power. The wire from the fuse panel to the switch is fused, both fuses are good but no power to the switch. I simply put a hard wire from the panel to the switch and all is good. Pumps are running again.'

So, the next question is the pink/black wire, where should that really go. The Inertia switch looks to be untouched and in good condition just by looking at it.

Thanks again.

bossbob · Dec 29, 2017

New Issue,

I can hear the pump run, the engine starts when cold, but tends to crap out after a few minutes. Like it's starving for fuel. Won't hold a solid idle, want's to jump around, and has no power.

I depressed the schrader valve and it has pressure, will have to rent the tool to get a proper measurement.

But assuming I have good pressure, what should I look into first.

Shran · Dec 29, 2017

According to my diagram there are two wires at the interia switch - pink/black, and orange/light blue. Pink/black can either go from there to the tank selector switch if you have dual tanks, or straight to the positive side of the fuel pump. Orange/light blue goes from the inertia switch to the fuel pump relay.

Sounds to me like your in-tank pump is not working and the high pressure pump is locking up from the added strain of pulling fuel all the way from the tank. I have had this problem a few dozen times. Could be something else though. Get a fuel pressure reading.

bossbob · Dec 30, 2017

Ok, initial test shows 36 psi with fuel pump on, and engine off.

28 psi with engine on.

Short revs bring psi above 30 and settles back down to 28 psi

What should I check next.

I'm letting it run for awhile to see if any changes happen while it's warming up

alwaysFlOoReD · Dec 30, 2017

bossbob said:
New Issue,

I can hear the pump run, the engine starts when cold, but tends to crap out after a few minutes. Like it's starving for fuel. Won't hold a solid idle, want's to jump around, and has no power.

I depressed the schrader valve and it has pressure, will have to rent the tool to get a proper measurement.

But assuming I have good pressure, what should I look into first.

I had an 86 with the same symptoms as you, I never did get it sorted before it died.
Check all vacuum lines.
Clean and check IAC valve.
I don't believe there is a maf so no wire to use cleaner on.
Probably the O2 sensor is end of life, change it out.

bossbob · Dec 30, 2017

After about an hour of idling and running the truck around the block, the PSI came down to 10 and crapped out. Turned everything off for 15 minutes and tried it again, fuel is back to 30 psi but only held for about 3-5 minutes and back to 10 psi and stalled out.

I can clearly hear the frame pump running and it seams to struggle or load up when the pressure drops.

With todays testing, would you say it is the in tank pump that is crapping out.

Or should I run more test to narrow it down.

Thanks again

alwaysFlOoReD · Dec 30, 2017

It's not too hard to buy a fitting for the inlet side of the frame pump. Buy enough fuel line to reach a jerry can and try running that. I believe the fuel pump will pull enough to start flow and then you can see if the pressure is different now [while running]. If no different pressure then the frame pump needs replacing.
I've also used a pop bottle, drilled a slightly undersize hole in the lid, feed in the fuel line and then hang it upside down to gravity feed the high pressure pump.

holyford86 · Dec 31, 2017

One thing you could also check is the canister filter, this should be right ahead of the tank inside the framerail. There was a recall on these back in the day due to leakage and the fix ford had was to remove the filter from this housing and add a fuel filter on the engine side of the framerail pump. My 86 never had this done to it and the additional filter was missing, meaning it still had a filter in the canister. I had run into similar issues back in the day and found that the filter was clogged and had disintegrated partially. Another thing to check is the fuel pump grounds, I've had them rot and cause issues like this. Also pull the vacuum line off of the fuel pressure regulator and cycle the key a few times, if fuel runs out then the regulator is shot and needs replacement. Also check the fusible link driving the relay, when they burn out there is no outward symptom usually, this causes people to cobble in switches like you have found, a resistance check between the wire connection at the starter relay and the green fuel pump relay base will check for this.

bossbob · Jan 10, 2018

Haven't touched it since the last post, but the holiday's are over, and company is gone. So, time to get back to the fuel issue.

Does this car have an OBDII plug that I can run codes?

What are the chances it's just a bad fuel filter. We just got the truck a few months ago, and I think the PO only used once in a while. Should I be able to hear the pump in the tank run?

THanks again for the help, hoping to get some time on it this weekend.

85_Ranger4x4 · Jan 10, 2018

It is OBD1, the connector should be under the hood.

alwaysFlOoReD · Jan 10, 2018

85_Ranger4x4 said:
It is OBD1, the connector should be under the hood.

Yep, under hood passenger side in corner where inner fender and firewall meet. It can be buried under stuff but is usually easy to find. It's a polygon shape, a squished rectangular 6 sided plastic piece and could have a cover. About 3/4"x2".

DanInVA · Jan 11, 2018

I would say that the chances of a plugged fuel filter are unlikely. If the fuel filter were plugged, it would never run, rather than dying out when the pumps get hot.

Do you have a DVOM? If you can get a hold of a wiring diagram, you may be able to ohm the fuel pumps at the connectors. When the pumps get hot, you may be able to see an increase in resistance on the bad pump vs their resistance when they are cold.

Sent from my SM-G920V using Tapatalk

86 Ranger, fuel delivery problem

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