Chev Fuel pump relay 15528707

07-23-2011, 09:58 AM

Steve VW

Those of you with late 80's Chev chassis will have a "hybrid" fuel system. (Mechanical fuel pump and carb but also an electric pump in the tank.) The pump is run by the fuel pump relay GM 15528707. (see the 1996 Chev Motor Home guide Appendix 7-7 page 7-44 to 7-46)

The relay has 2 functions: it supplies power to the fuel pump during cranking and while running but shuts off if oil pressure is lost. Also it supposedly has a delay timer to cycle the pump for 5 seconds prior to startup. (This, and the color coding for the relay, from page 7-46)

Bad news: this relay is required for engine operation, prone to failure, the part is not available anywhere I know of, and the relay diagram is vague about which wire does what inside the relay.

Good news: it's just a standard single pole (5 wire) relay with a timer inside.

My Barth was slow to start after sitting due to dry carb bowl. I have manual fan switches to run after shutdown to reduce heat soak but carb still needs priming. Inspection of the relay (a tight fit under the forward left side of the doghouse near AC compressor and too tight for pics, sorry) revealed an empty relay case attached and another relay hanging from the wires. My relay did not have the 5 second cycle working. Search for replacement was dead end.

To take care of both problems I replaced the relay with the generic 5 pole type (same as the headlight relays, fan switch relay, etc.) I also added (dashed lines in drawing) a normally open switch to trigger the relay for manual priming. After sitting for some time, I hit the prime button about 15 sec and the engine started promptly!

If relay 15528707 fails, you'll need this info...
The black and dk blue wires are interchangeable.

07-24-2011, 08:31 PM

Doorman

Bad relay may not be your only problem. your Qjet may be leaking fuel out of your fuel bowl thru the plugs on the bottom of the carb (common problem on Qjets). Not only leaves no fuel in bowl, it also will wash down cylynder walls. and will draw a little fuel while running. Common fix is to clean plugs with brake clean, then use JB weld to fill plug holes while carb is upside down. If this has been going on for a while it might be a good time to rebuild the Qjet. while it is off.-dry fuel bowls are hard on accelerator pumps.(dry hard pump cup).
Doorman

11-10-2020, 06:30 PM

BarthBluesmobile

I will quote from another forum on rv.net!

"I found another maker for the FPR used in older P30's, it is Airtex and the part number is 1R1240. It is an exact replacement for the OEM, TRW 15528707 relay."

11-10-2020, 07:48 PM

Jim and Tere

quote:
Originally posted by Steve VW:
Those of you with late 80's Chev chassis will have a "hybrid" fuel system. (Mechanical fuel pump and carb but also an electric pump in the tank.) The pump is run by the fuel pump relay GM 15528707. (see the 1996 Chev Motor Home guide Appendix 7-7 page 7-44 to 7-46)

The relay has 2 functions: it supplies power to the fuel pump during cranking and while running but shuts off if oil pressure is lost. Also it supposedly has a delay timer to cycle the pump for 5 seconds prior to startup. (This, and the color coding for the relay, from page 7-46)

Bad news: this relay is required for engine operation, prone to failure, the part is not available anywhere I know of, and the relay diagram is vague about which wire does what inside the relay.

Good news: it's just a standard single pole (5 wire) relay with a timer inside.

My Barth was slow to start after sitting due to dry carb bowl. I have manual fan switches to run after shutdown to reduce heat soak but carb still needs priming. Inspection of the relay (a tight fit under the forward left side of the doghouse near AC compressor and too tight for pics, sorry) revealed an empty relay case attached and another relay hanging from the wires. My relay did not have the 5 second cycle working. Search for replacement was dead end.

To take care of both problems I replaced the relay with the generic 5 pole type (same as the headlight relays, fan switch relay, etc.) I also added (dashed lines in drawing) a normally open switch to trigger the relay for manual priming. After sitting for some time, I hit the prime button about 15 sec and the engine started promptly!

If relay 15528707 fails, you'll need this info...
The black and dk blue wires are interchangeable.

Steve, how can you tell you have an in-tank fuel pump? Tere has looked at the wiring and the only thing she sees is the wire that goes to the fuel pickup.

11-10-2020, 10:00 PM

Steve VW

I believe GM used intank pumps on the P30 chassis from about 1986 on. At the top of the tank there is a circular plate that mounts into the tank. The plate supports the pump. There are two wires: one wire for the gauge and another wire for the fuel pump. (Actually there is also a ground wire too)

There are three steel hose barbs, one for the fuel being pumped out, one for fuel line return and one for a vent.

see here: https://www.barthmobile.com/eve...423906387#2423906387

11-11-2020, 07:24 AM

BarthBluesmobile

It took a bit to remember it all, but the sender unit in the tank for me is FG12X.

https://www.barthmobile.com/eve...061/m/7263975367/p/2

I have a picture of the top of the sender there.

Matt

11-12-2020, 12:55 PM

Doorman

You should find the fuel line to the engine pump runs from a fuel regulator on the frame and not the fuel tank. Your coach should have in tank pump.

11-14-2020, 05:39 PM

Jim and Tere

Decided to get under the Barth today. At 82, that's a big decision because one never knows if they can get back up again. Found the fuel regulator, ergo there is a fuel pump. Tere's mantra is 'what can I take apart today?', so I guess she'll eventually drop the tank and do her thing. Done it on Old Blue. Will be much easier with leveling jacks to raise the Barth up for jack stands. Doris sure did a nice job with chassis saver under there.

Jim (aka Hum)




	1985 Regal 29' Chevy 454 P32 8411 3172 29FP3B Gear Vendor 6 Speed Tranny