you'd also think if there was a short in a wire the rain would make it worse too.
Great that just threw every theory i had out the window

 

You need to take a fuel pressure reading off of the fuel rail. On my '85 F150, 302, the fuel return line to the tank was pinched off, behind the driver's side valve cover, near the fuel pressure regulator. It drove me nuts trying to locate the fault because on my truck there was no fuel pressure connection fitting on the fuel rail, so I was unable to take a reading. I finally discovered it when I proceded to take the upper intake manifold off to check for vacuum leaks. There are two fuel lines that connect to the fuel rail, near the firewall. One of these is the fuel supply line from the tank, the other is the return line.

Good luck!
Norman C

 

im afraid he's taken fuel psi readings about 3 times the last one is

plus he said that the truck ran near perfect when its raining
personally i dont think thats a fuel line problem.. but you never know

 

No word from the garage yet. I need to ckeck in today or tomorrow to see whats going on. I'm leaning towards the wiring harness. I think that's the only thing that hasn't been replaced yet. ???? Oh well, we'll see. Have a great day everyone.

Todd

 

good luck you got urself a doozie of a problem here

 

Kart how sure are you that you got the right in tank pump unit? How long after you installed the new pump did your problem start? 87, 88, and 89 use the DFR and the in tank fuel pumps are different from what I understand. the 90 and up have some sort of check or diverter valve on the in tank pump unit. Try bypassing your DFR but use the tank you didnt put the new pump in. When running down the road and the missing/jummping starts have you ever just pulled over to the side of the road and see if you smell gas or see it leaking on the ground?

 

I had this problem before the new sending / pump was installed. It runs the same on both tanks - before and after the install. I've never pulled over and looked for anything.

Todd

 

What's the chances I have a bad relay? Fuel Pump Relay or Ignition Relay. Is there a way to check them?

Thanks Todd

 

I thought the relays had been replaced. It would not hurt to replace the relays on a truck as old as yours. Also, check the wires and fusible links that go to both relays. Heck, make sure the relay sockets are clean and not damaged.

 

It's in the wiring harness somewhere. I talked to the guys at the garage on Friday and they told me they know what's wrong with it now they just need to find it. Apparently they hooked up the voltage meter to the 02 sensor and by moving the wiring harness around the voltage changes. So they are figuring that there is a bad spot in the wiring somewhere in the harness. Interesting. I guess the rain and dampness (acting as a conductor) is why it ran better. Any comments on this? I sure hope this is the problem and they get it done and that's it.

How much is a wiring harness?
Where do you get one?
How hard is it to change out?
Would it be a good idea to just change the whole thing or just fix this problem?

Thanks, Todd

 

Where has everyone gone? Hunting?

Todd

 

If you want a new one you should look at painless performence

i dont think they have a stock replacement but i bet you could send in the old one and they could make a new one.

however id just recommend replacing the section of wire that goes to the O2 sensor as far back as possible

 

Yes, troubleshoot the harness. I repaired the one on my 1987 F250 after it had been damaged by fire (previous owner). It was easy to do and there really isn't all that much there.

The local junk yard wanted $30 if I pulled it.

You'll see that Ford uses sections of harness in the engine compartment. The engine harness is extremely easy to repair or swap.

 

Thanks for the advice. They told me at the garage that they were going to replace the 02 sensor wire. So, I'll just let them do that for now and see if that takes care of the problem. Have a great day.

Todd

 

good luck
hope it works