1988 f250 4x4 460 manual transmission. Originally fuel injected but was converted to holly 4 bl. The wiring on this truck is a nightmare. I have put new pumps in the tanks and installed a 3 port fuel selector. When I try and power the pumps thru the relay I can't get the power to the switch. If I jump the yellow to brown at the relay everything works. For some reason the relay is not closing for some reason. (Remember the wiring is a nightmare. The fuel relay was missing. And lots of cut wires). The ecu may be bad. I don't know. Anyway I'm looking for another place to power the pumps from. It needs to work off the ignition I think. Any suggestions?

 

What ignition system are you running on the truck?
(DP2 or EEC 4)

 

Not sure what your asking. It's using a distributer and coil. Is that what your asking?

 

That should have read DS2 & EEC4.
Both systems use the distributer and coil.

Most DS 2 (Dura Spark) systems with a carb use this way of controlling the electric fuel pumps:


The EEC4 systems use this system, they are FI and no carb:


You would not use the high pressure pump on the frame but are you trying to use this rest?
/

 

The truck is wired using the eec4. It looks like trying to change would be too big of a job.
So is there a way to power the brown wire going to the inertia switch? For instance can I pull power from the coil? This truck is not going to be used on the roads.It will not see 30 mph the rest of its life. I will use it in Alaska on a beach. I just want it to run.

 

I would ground the wire for the fuel pump relay coil. The one that went to the self-test connector (tan wire with a light green stripe), this wire also goes to pin #22 of the computer.
Then when you turn on the key the power relay will pull in and power the coil of the fuel pump relay.

 

Will this work even if the computer is bad?

 

Rant warning.

Every time I see someone has removed a perfectly good EFI system in favour of a carburetor, I feel sick. WHY ARE YOU DOING THIS!!!!!!

Don't give me "reliability" or "More power/tuneability" because IT JUST AIN'T SO! If you don't understand how it works, leave it alone or learn about it. You need to know how EFI works even if you propose to change to a carburetor because you must use an entirely different fuel delivery system. Fuel pressures and pumps are different, the ECM is no longer required and it will involve extensive rewiring and replumbing to even get close to anything workable, let alone support because no one will know exactly how you worked around all the issues of such a conversion.

Rant over and I feel a little better. My apologies, don't mean to offend, but I had to get that out of my system.

So, exactly how are you delivering 5 lb fuel pressure to the carburetor? If an electric pump is in the mix, the circuit subford supplied is correct. Are the new pumps correct for a carbureted engine? The EFI pumps will deliver too high a pressure, even the in tank lift pumps for an EFI engine with the high pressure pump on the frame rail will make around 8 lb. You mention a new selector valve. Does this incorporate the electrical switching for the in tank pumps and the fuel gauge?

The ECM is entirely out of the picture with a carburetor as far as fuel control goes. You should be running the DS 2 ignition system because the TFI or EDIS systems require a signal from the ECM for advance. Since you trashcanned the EFI system, all the inputs required to calculate SPOUT or SAW for ignition control are gone and you will be limited to the "limp home" setting of 10 degrees initial advance. So much for the economy and power, (sorry, starting to rant again).

Anyways, I understand this does not have to measure up to regular use, so you may be OK with it. Hope I have at least added a few points to check.

 

Thanks for all that rant, but if you had read any of my previous posts you would see that I am not the ******* who destroyed this truck. Im the guy trying to resurrect this truck. When i got the truck (cheap), only 1 tank was working and that was the rear. The guy had plumbed it using the return line to a small frame mounted inline pump and from there a piece of air hose to the carb. Now I have new intank pumps which should be all the pressure I need for the carb.
Also where would I look for the DS2 ignition system?

 

Thanks for understanding!

Really not directed at you, rather the next guy who reads this and starts to think, Hey, maybe I should ditch my EFI in favor of a carburetor. Read it on the Internet, so it must be true.

DS 2 is best identified by the vacuum advance on the distributor and the module on the inner fender. No vacuum advance and you have TFW or EDIS.

You are so right on previous owners and the mess you often inherit. You are also right that I have not read your previous threads and do not know that was your situation.

Can't read them all! Best of luck.

 

Thanks, I am going to out to work on the truck in about an hour. With any luck Ill have a running truck. Then I can start on several other issues like a cracked firewall that was never disclosed. Guy tried to tell me it just needed fluid. Ive all ready got the repair bracket in hand.

 

You probably won't have the oil pressure switch in Subford's diagram. You could start it with the circuit bypassed, but it is an important safety feature. The fuel pump relay and inertia switch are similar to the EFI circuit, so you probably could use what you have. Inertia switch is equally effective before or after the fuel pump relay. ECM provided the ground to the relay. You could bypass this permanently to ground at the test connector. If you feel creative, you could place the oil pressure switch in the ground side of the relay coil circuit. Would work just the same and you could leave the rest of the fuel pump relay circuit as is.

 

Yes, the power relay is only controlled by the ignition switch (key) and has nothing to do with the computer.
With that wire grounded the computer will no longer have any controlled of the fuel system and the selected fuel pump will run all the time the key is on.

 

I'm going to try that. I already tried to self test the pump by jumping hole 6 with hole2 and that produced nothing. That's what makes me think the computer is bad and maybe what started the destruction in the first place. When I started tracing the wiring I found another selector switch under the dash. There was nothing wrong with the original switch.

 

Yup, ignition will control the positive side of the relay and the ECM used to control the negative side of the relay with the original EFI application. Grounding the test point bypasses ECM control, but you still have ignition control.

Just a note on that oil pressure switch, it must close when oil pressure is present and open when pressure drops. An idiot light sender has exactly the opposite logic and will not work. Best to find the part # applicable to subford's diagram. Fuel will shut off when the engine is not running. This can be a problem when the carburetor is dry as you need to build oil pressure to start the fuel pump. One solution would be to add a bypass relay for the oil pressure switch activated by power to the crank circuit.