twoweeks1

OK I have posted the "Truck will not go above 2300RPM" It did better today but not good I checked all the mechanical linkages everything was fine . It is warmer today 30 degrees so i had a good idea it was tempeture related I then went to the Haynes Manual and it also said to check the fuel heater Which in the book it listed everything the truck was doing , And you know what? there is a relay but no wires going there, They must have gotten disconnected during the plate install, it is the only thing I can think of. The other relay (one on ther right) has wires comming out of the main harness just to the right of it. I cannot see any other plugs. I looked around the filter housing down low and i dont see any other tails comming from the main harness that runs across the cowl on that side of the engine except the shutdown relay wires . I looked at the lift pump area and there are wires comming from the bowl which is what the book shows as the fuel heater, I can follow them to a connector about 4" then they go up into the main harness where they are all factory taped, but no other plugs. I have a fuse in the fuel heater slot in my fuse box under the hood, so ther has to be a harness right? I crawled underneth and didnt see anything. Can someone look at their relay There are two relays mounted on the firewall high just to the right of center ( the one on the left is the fuel heater relay ) and tell me where the harness is comming from? if on theirs they come from the same place as the fuel shutdown relay(the other relay)wires come from. Thanks Wayne :

CarlJensen

On my 95 the harness comes out from under the cowl area. The harness runs in back of the rubber cowl seal right next to the other harness.

twoweeks1

the harness should be there right?

infidel

No after '96 the fuel heater relay on the cowl was discontinued. Your '98 has the relay in the underhood fuse box. If no wires are going to the fuel heater they likely overheated and melted (common) someone may have cut them out and pulled the relay.
The fuel heater won't make any difference in starting whatsoever unless your fuel is starting to gel. It's purpose is to melt gel particles so they can make it through the filter. If you are using winter blend or additive you shouldn't need the heater at all until temps get below minus 35F.

twoweeks1

well I'm confused I do have a pair of relays on the firewall. the one on the left is not plugged in, in my haynes manual it stated that this was the fuel heater relay. all odf the symptons i am having it listed as a result to this part malfuncting. But I cannot find the harness that plugs into it. I thought this was causing my problem it definatly runs different(better) in 30 degree weather vs 20 degree weather. What other part failure would cause this and be tempeture related. My truck runs terrible something has went bad.Please read my "truck will not go above 2300RPM" post and give me any other info

infidel

Have you cleaned the screen in the fuel heater?
Checked the fuel pressure or changed the overflow valve?

KWentling

There was a recall on my '98 12-valve for missing fuel preheater wiring. You should check to see if you're truck was one that was recalled. Infidel is right about the heater relay being in the PDC and not on the firewall. Mine had the relay there too and had me confused also. I got to look at the recall wire installation instructions and it definately comes from the PDC and not the firewall. DC must have not changed the wiring loom. Even my '98 service manual shows the relay on the firewall but that isn't correct. I thought the tech doing my recall didn't know what he was doing untill he showed me the instructions from DC.

Kim

twoweeks1

Hello, There is also a relay in the fuse box (DUH) it is clearly labled. There is one on the firewall also I guess they ony had the shutdoun relay as a combo piece, when they assembled it. It turned out to be the overflow valve on the injection pump.. Thanks for everyone who gave their input it helped alot Wayne

KWentling

The"fuse box" you refer to is the PDC (Power Distribution Center). Glad you found you're problem.

Kim