1987 F250 460cid fuel problem
 

My rig - 1987 F250, duel fuel tank - both 19 gal steel tanks, fuel tank selector switch, electric in tank pumps, what appears to be a fuel pressure regulator by the distributor with 3 fuel lines (the supply line from the tanks/pumps, the return line, and supply to carb line), and a Edlebrock 1405 carb (works fine, floats properly adjusted, etc).

2 problems I'm looking to solve:

1) the fuel in the - supply from pumps line - bleeds back to the tank after appx 24 hours of not running the engine, and it takes a long time of cranking for the pump to get fuel back to the carb and it to fire up. It initially fires, just about immediately uses the fuel in the tiny carb bowls, then has the long crank (15+ seconds)until fuel arrives and then it starts reliably. Does this with either tank selected.
-> Looking to learn what device keeps the fuel from bleeding back to the tank - I'm assuming via a check valve or something - to know what to replace. I would think either what appears to be the pressure regulator or the tank selector switch (the one with the fuel lines running thru it) but don't want to start shotgunning parts... I'm open to replacing with other than OEM parts...

2) the front fuel pump is dying - it's intermittent but the wiring is good.
-> looking for good experiences with replacement pumps that have proven reliable.

OK if you have info on either I really appreciate it!

My 87 didn't have electric pumps, mechanical type on engine so can't say as real familiar with the in tank pumps that year.

You said the fuel in line runs back to tank and need crank it for a long time to pump fuel back up to carb.

Sounds like might be oil pressure issue over any fuel system problem.

Reason you can't simply turn the key to run, allow pump to prime before attempting start would be use of oil pressure sense relay. Safety thing, No engine oil pressure = engine not running = no fuel pumped.

Needs oil pressure to pull in relay to energize fuel pump.

Hows the oil pressure? build quickly? or high mileage so very little now days?

Maybe a manual switch trigger oil sender relay, ensure pump runs when key is turned to start? Short delay allow oil flow then throw switch fire it up. Once running turn off switch, now has sufficient oil pressure to hold relay closed.

I'd check the oil pressure and the oil pressure sending unit too.

Something other then float bowl inlet valve prevent drain back? Nothing coming to mind, did you verify the bowl is full cold start up? Or is it drained back and empty too?

Sounds more to me like the carb is leaking fuel into the cylinders.

Good questions danr1! - I'll check the oil pressure switch (know 'bout the pressure sender for the gauge, didn't know there was a switch also) & will update in a day or two when I can wrench on the truck again.

Digging a bit, found a google link to an Edlebrock 1405 installation manual that has this note:
"NOTE: Some late model Ford 460 engines are equipped with hot fuel bypass units. It is necessary to replace the stock unit with Ford #E3TZ9N176B (with blue dot) which has a 0.040" orifice."

This appears to be what I was thinking was the fuel pressure regulator but is a hot fuel bypass unit. The google searches indicate the stock unit is related to fuel starvation issues, I am assuming I have the stock one, but could not find a source to this "blue dot" unit. Mine has no "dot" on it that I can see...

A search for the blue dot unit was unsuccessful, anyone know where someone can buy one? - or can an adjustable/very low pressure regulator with return line be used instead?
The Edlebrock manual sez "Do not use more than 6.5 psi fuel pressure."

Thx!

Sorry wasn't trying to imply there was a switch just that might be simplest fix, if motor just doesn't build oil pressure fast enough these days, install a manual switch to close relay until motor is running. At that point you'd be able to turn off the switch, retaining that safety feature.

Easy enough to test for the issue, test for power to the pump while attempting to start it cold, after sat all night.

If gets power right away, couple seconds of the motor cranking then you know that is not the problem.
Same token if doesn't get power even after 30 - 45 seconds, longer? after motor has been cranking over? its just not building oil pressure fast enough, or has a bad oil pressure sending unit. Maybe little of both conditions?

Another thing to check out, how much fuel pressure does the pump deliver, within spec? Spec 6 to 8 lbs.

The orifice thing, depends on if this is a recent problem or always been an issue after your had installed that carb?
If it ran and started up right with it before? this is a new recent problem? then the orifice isn't the problem.

Good questions, hopefully on Thurs I can watch the oil pressure to see how quick it comes up, also see when the selected fuel pump actually gets power. This is my backup vehicle so I don't drive it that much so it may be a day or two.

The motor has appx 160k miles by the way, oil pressure is good when it's running & doesn't burn much between oil changes (1/3 to 1/2 qt) - though it would be happier with new valve stem seals.

I'll have to pick up a fuel pressure gauge & see what the pressure is from the pumps and from the hot fuel bypass unit.

I bought this truck in Mar of this year, it already had the Edlebrock carb on it and it has had this issue since I bought it so don't know if the issue began with the carb install...

I like the idea of installing a switch and relay to test and to prime it instead of cranking for so long, don't have schematics, know of any sources (especially something like an oem service manual on CD)?

I'm thinking the hot fuel bypass unit may be a strong contributing factor, and am wondering if just replacing it with a pressure regulator would be a good idea?

Thx!

OK, oil pressure sender shows normal (middle of the gauge) oil pressure in 1 to 2 seconds of cranking so it looks like oil pressure is good.

I found that there is in fact an oil bypass switch separate from the sender - and it is inline with the fuel relay energizing circuit - haven't determined if the switch is good or not. None of the local parts stores (NAPA, Checker, AutoZone, etc.) have a listing for this switch - would like to find out the ford and aftermarket part numbers.

I did find that the wiring of the power source to the fuel relay energizing circuit was modified by some PO and was reading well under Batt voltage - was reading 8 volts, hmmm, corrected that...now is Batt voltage

I found an RV blog that discussed that the "I" terminal on the starter solenoid bypasses and basically hot jumpers the oil pressure bypass switch so that the fuel pump relay is always energized while cranking and so fuel pumps are always running while cranking - anyone know if this is true for the F series also?
Perhaps I need a new starter solenoid just for the "I" circuit - will check this in a couple days...

I also found that my fuel bypass valve was an aftermarket one, the Ford #E3TZ9N176B has just arrived and I'll install it in a couple days.

I have found that the fuel tank vent line goes straight to engine vacuum and after a while of driving creates quite a bit of vacuum in the front fuel tank - need to fix this - most all the egr, vacuum lines, and other smog controls were removed by a PO by the way.

Anyone know how someone would setup a simple (and safe) fuel tank venting system in the absence of the original OEM setup?

Also, it's really difficult to troubleshoot without schematics - the ones in Clymers, etc., are pitiful especially for this year 460 - anyone know where I can get OEM ones?

These issues appear to all be related to the issue of long cranking before carb gets fuel - all are involved with the fuel delivery system anyway...thx...

Hey I know this is and old thread but it's hard for me to find anyone that has had an 87 F250 with a 460 and a mechanical fuel pump with duel tanks of course.
My carb is not getting fuel and I cant figure out why the switch isnt working. Plenty of oil pressure.

Did you mean electric fuel pumps? If you really do have a mechanical fuel pump I don't know as I have electric pumps - mechanical just pumps when the engine is turning without anything electrical involved (to my knowledge). If you do have electric pumps I can help as I have mine working now...

Your issue is the subject of several Ford TSBs......check valve is a likely culprit along with your "out of tank" dual port selector and pump assembly........

:-X22

But he does not have any of those items on his truck.
He does mean a mechanical fuel pump and no pumps in the tanks like the diesels have but his is a gas truck.

The oil pressure/switch has nothing to do with the pumping or the tank selection with the mechanical fuel pump fuel system.

Would that check valve be in the dual port selector - the switch that selects the fuel tank? Any links to the tsb's in question? - thx