86 E350 Fuel Issues

[NotmyE350]

My Sister has an 86 E350 motorhome with the 460 and dual tanks. It's been sitting over the winter and has been having a 'lack of fuel' issue since last summer. They've had the rear fuel pump replaced and the carb rebuilt last fall but there's still an issue with fuel delivery. The mechanic they brought it to (after the $1600 repair bill) has said it's an electrical issue.

I went to check it out for them last weekend and found that even with the oil pressure switch jumped, the fuel pumps aren't working (switching between tanks). I've checked for voltage to the motorized switch near the front tank, there's 5-7 volts at one pin but the rest are 0. I'm assuming the 5-7 volts is the signal to the fuel gauge. I've checked the inertia switch on the passenger side and it's got continuity and is getting power with the key on.I was trying to locate the tank selector relay to check it but have no idea where it might be.

Does anyone know where Ford hid it?

Kyle

[Gary Lewis]

Kyle - First, don't let anyone tell you that this is a site for Bullnose trucks and an E-Series van doesn't qualify. Just go ask the guys with van-based RV's who are active on here.

However, we don't have the E-specific wiring diagrams. Ours are pickup and Bronco diagrams. So I can only assume that the vans might be wired the same.

I put together this page (Documentation/Fuel Systems/Fuel Systems Wiring) that attempts to lay out how the Bullnose vehicles are wired. Maybe that will help.

As for the tank selector relay's placement, on a truck it is on the driver's side of the firewall under the hood, just outboard of the brake master cylinder. And there are two versions - one with the relay in a holder along with another relay, and one with the relay screwed to the firewall by itself. The page below from the 1986 EVTM shows the version in the holder.

As for the 5-7 volts, that is probably the signal to the gauge, but if it is it should be pulsing. The oil pressure, coolant temp, and fuel level gauges are driven by the Instrument Cluster Voltage Regulator, which is a misnomer if ever there was one, and it just gives pulsing voltage to the gauges. So the signal from the sender to the gauge should not be steady on your meter.

Hopefully this will get you started and we can troubleshoot some more.

[grumpin]

Kyle - First, don't let anyone tell you that this is a site for Bullnose trucks and an E-Series van doesn't qualify. Just go ask the guys with van-based RV's who are active on here.

However, we don't have the E-specific wiring diagrams. Ours are pickup and Bronco diagrams. So I can only assume that the vans might be wired the same.

I put together this page (Documentation/Fuel Systems/Fuel Systems Wiring) that attempts to lay out how the Bullnose vehicles are wired. Maybe that will help.

As for the tank selector relay's placement, on a truck it is on the driver's side of the firewall under the hood, just outboard of the brake master cylinder. And there are two versions - one with the relay in a holder along with another relay, and one with the relay screwed to the firewall by itself. The page below from the 1986 EVTM shows the version in the holder.

As for the 5-7 volts, that is probably the signal to the gauge, but if it is it should be pulsing. The oil pressure, coolant temp, and fuel level gauges are driven by the Instrument Cluster Voltage Regulator, which is a misnomer if ever there was one, and it just gives pulsing voltage to the gauges. So the signal from the sender to the gauge should not be steady on your meter.

Hopefully this will get you started and we can troubleshoot some more.

I was in this system a lot a couple of years ago. Just did a quick check and I’m pretty sure there is no relay in 86. Van could be different. 86 has the tank selector switch and the tank selector valve.

My problem was intermittent fuel cut out, it was the oil pressure switch connector. You’ve checked that. Might have to trace wires and connectors, and of course always check the grounds.

Also, Fuselinks, the Inertia switch and the Fuel Pump Relay.

[NotmyE350]

Kyle - First, don't let anyone tell you that this is a site for Bullnose trucks and an E-Series van doesn't qualify. Just go ask the guys with van-based RV's who are active on here.

However, we don't have the E-specific wiring diagrams. Ours are pickup and Bronco diagrams. So I can only assume that the vans might be wired the same.

I put together this page (Documentation/Fuel Systems/Fuel Systems Wiring) that attempts to lay out how the Bullnose vehicles are wired. Maybe that will help.

As for the tank selector relay's placement, on a truck it is on the driver's side of the firewall under the hood, just outboard of the brake master cylinder. And there are two versions - one with the relay in a holder along with another relay, and one with the relay screwed to the firewall by itself. The page below from the 1986 EVTM shows the version in the holder.

As for the 5-7 volts, that is probably the signal to the gauge, but if it is it should be pulsing. The oil pressure, coolant temp, and fuel level gauges are driven by the Instrument Cluster Voltage Regulator, which is a misnomer if ever there was one, and it just gives pulsing voltage to the gauges. So the signal from the sender to the gauge should not be steady on your meter.

Hopefully this will get you started and we can troubleshoot some more.

Thanks Gary/Dane,

yes the fuel gauge voltage was pulsing, like you said, between 5 and 7ish volts.

I'll have my sister take a pic under the hood to see if the relay is there. Unfortunately there was a mouse nest under the hood so that may be the issue there.....

[ArdWrknTrk]

Kyle,

I'd start with fuse 18 (or whatever the equivalent is in an E-series)

Without power coming to the oil pressure switch in start and run you're not going to close the fuel pump relay.

[NotmyE350]

Kyle,

I'd start with fuse 18 (or whatever the equivalent is in an E-series)

Without power coming to the oil pressure switch in start and run you're not going to close the fuel pump relay.

Thanks for the replies, I'll have to do some more checking, work from the fuse box back. Hopefully the mice didn't munch on something.

 

[old55pete]

Thanks for the replies, I'll have to do some more checking, work from the fuse box back. Hopefully the mice didn't munch on something.

Keep in mind too, that the chassie was built by Ford but the folks that built the camper on it will move things around to fit their needs. I have found the tank valves moved all of the way back by the rear tank instead of on the frame by the drivers door. I have also seen the wiring harness has been changed/ extended and the wiring go all of the way to the back of the chassie and loop back to the valve on the frame under the drivers door...……...just a heads up.