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sarge1946 · 06-28-2022, 07:15 AM

2007 W24 workhorse chassis.
No power to fuel pump relay when ignition is turned on!

MrMark52 · 06-28-2022, 08:28 AM

See page 1160 pr book 6 of the Workhorse chassis manuals, page 1160 (for 2007 models is the one I have). Wiring diagram can be found in the Workhorse “2001_Workhorse_chassis_w_8_1_engine” guide for 2001 models. I don’t think a lot would have changed for your coach as my ‘91 P30 Chevrolet coach was exactly the same.

The fuel pump relay is powered thru the PCM and fuse #39 powers the contacts which then power the fuel pump. It energizes the FPR for 2 seconds and if it doesn’t see ignition pulses (meaning the engine is running) it kills the relay.
I believe fuse 39 is in the engine bay opposite the under dash interior fuse block under the dash.

sarge1946 · 06-28-2022, 12:37 PM

Thank you MrMark52!
I changed the relay and I can feel it coming on for a couple of seconds then shutting off. During this process there is no fuel (rail) pressure. I need to check if power is actually getting to the fuel pump. I am trying to exclude all possibilities before replacing the fuel pump.
I do not have any manuals or fuel system wiring schematics.
Do you know if I am able to access the information on line?
Not very computer savvy!!!!
Thanks SARGE.

edgray · 06-28-2022, 02:20 PM

Quote:

Originally Posted by sarge1946

Thank you MrMark52!
I changed the relay and I can feel it coming on for a couple of seconds then shutting off. During this process there is no fuel (rail) pressure. I need to check if power is actually getting to the fuel pump. I am trying to exclude all possibilities before replacing the fuel pump.
I do not have any manuals or fuel system wiring schematics.
Do you know if I am able to access the information on line?
Not very computer savvy!!!!
Thanks SARGE.

There are numerous resources HERE: Workhorse Technical Info. Just be sure you chose the correct model and year for your chassis.

MrMark52 · 06-29-2022, 05:37 AM

Thanks to Ed Gray for the links!

When you get the wiring diagram manual, it shows a connection point for the factory to use that plows initial charging of the fuel lines when the chassis is built - basically a bypass for the PCM.
We had an ‘01 Tahoe that the fuel pump failed. It was our first multi-port fuel injection and fuel pump failure. After dropping the tank and replacing the fuel pump I couldn’t get the engine to start. I didn’t know about the pump delay.
After a few tries, I finally thought to get out and depress the port on the fuel rail, and got air. It took a couple of attempts before I got fuel. Never a problem after that.

sarge1946 · 07-01-2022, 06:55 AM

Thank you for the info link MrMark52.
Now I am kinda confused about which chassis I actually have.
The pasts supplier says the 10th digit in the vin needs to be a "7"(which it is) in order to
insure the right part. that would show to be a w24 chassis.
Owner"s manual says its a UFO R26, and diagram of the rear ccm fuse box cover and diagram on page 150 of the owner"s manual do not match.

edgray · 07-01-2022, 07:12 AM

Quote:

Originally Posted by sarge1946

Thank you for the info link MrMark52.
Now I am kinda confused about which chassis I actually have.
The pasts supplier says the 10th digit in the vin needs to be a "7"(which it is) in order to
insure the right part......

It is the sixth character in the 17 digit WCC vin # that indicates the chassis MODEL.

IF the sixth digit is a "3" or a "5", it is a P32 series chassis.

IF the sixth digit is "6" , it is a W-22 series chassis

IF the sixth character is an "A" , it is a W-24 series chassis.

The R-26 "UFO" rear gasser chassis is an " F "

There are other model designations, but the above are the most common ones.

The TENTH position is the code for the model YEAR.

Hope this helps. Ed

MrMark52 · 07-01-2022, 07:44 AM

Listen to Ed! :smile:

sarge1946 · 07-02-2022, 07:19 AM

Many thanks to MrMark52 and EdGray for your generous help!!
SARGE

MrMark52 · 07-02-2022, 08:44 AM

What chassis did you end up having?

The links Ed sent you are of great value - but there is also another manual that is a good study and maybe explains some things subsequently implemented or continued by Workhorse from when Chevrolet sold (or whatever) their chassis design to Workhorse.
Again, search the Files section of this site for “Chevrolet Motorhome Chassis Service Manual”. It was written around the P3X chassis, so if that is the one you have built by Workhorse, it will be of even greater help to you.