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Old 07-27-2021, 09:58 PM   #1
Join Date: Sep 2019
Location: Q
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Oil pressure switch bypass gone wrong

During the process of trying to figure out why I wasn't getting any fuel to my carburetor (which I am now after changing the fuel pump) I tried doing a oil pressure switch bypass there is a single wire going into the top of a bell shaped object that is connected to the oil pressure switch there are also 2 wires coming out of the oil pressure switch i put all 3 wires together and turned the key now I have no spark all 3 wires still light up my test light when I turn the key just like they did before but just turns over even when I prime the carburetor anybody know what happend they are goin to tow it in the morning I'm desperate please help
1987 holiday rambler motorhome 28' p30
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Old 07-28-2021, 04:48 AM   #2
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You’ve probably blown a fuse in the engine bay fuse block.

I no longer have wiring info on the P30 chassis or I would help more. You really need a wiring diagram to figure out if any fuses involved in the circuit as well as what happens when all those wires are connected together.
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Old 07-28-2021, 05:20 AM   #3
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Check the fuses on the GM fuse block. Most likely the ECM fuse. If you don’t have a test light, pull the fuses and visually examine them.
Steve (spinroch)
1997 Holiday Rambler Vacationer 31'
454 Chevy P30 FROG
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Old 07-28-2021, 09:13 AM   #4
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I am trying to remember this set up... I had several vehicles like this. It's really smart.. it's set up like this to prevent fuel pump from running if you have a fire.. I have been on several fires where this was bypass by owner.. so no matter how much water and foam we put on it.. it still kept burning because new gas was being sprayed in the fire.. it almost killed us.. so, trip down memory lane... that carb choke and fuel pump relay work off this.. oh now I and trying to think.. the system also keeps the carb choke heater from staying on,,, if there is no oil pressure.. that is whole other story.. so check this up on fuse box.. look for choke fuse, or gauges fuse.. if not there then hidden somewhere.. also look on driver's side, under hatch mounted on the sides.. there has to be relay.. look at carb.. where the electric choke goes.. there is one wire.. I had seen those get pulled out.. or short in choke.. just a warning.. ask operator if tow truck can pull driveshaft.. I don't know for certain.. but if you have a/p system and don't take off driveshaft you can pitch rv in trash.. tow truck will deny your claim.. or say you did not warn them.. so if you are not there to watch tow driver disconnect driveshaft and throw parts inside rv and lock it.. you are on your own.. good luck and let us know what you did and maybe better members then me will help you
2000 southwind storm, workhorse custom chassis with 7.4l vortec
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Old 07-28-2021, 09:18 AM   #5
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Have you had any problems with hard can, and follow all safety precautions.. you can take off air cleaner and hold down choke by hand... and someone crank and see if starts.. if does.. just gently let up on choke a little at a time ... slowly over 3 or 5 mins.. until eng warms up.. than get back with me.. and we can go from there..
2000 southwind storm, workhorse custom chassis with 7.4l vortec
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Old 07-29-2021, 06:41 AM   #6
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DonR is right about the fuel cut-off relay - i think it runs for 5-7 seconds and if it doesn’t see oil pressure, it kills the fuel pump.

And it’s use is specifically as he said - to kill the fuel pump in the event of a wreck.

That relay is typically mounted (was on ours) near #1 cylinder. 2 relays mounted side by side (don’t remember the reason for the 2nd relay).

There is a fuel pump test point coming off one of the relays. IIRC, you apply power to that TP and it will either power the relay or the fuel pump.

Supposedly that relay is NLA. Hopefully the smoke didn’t escape out of it. ��
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Old 08-01-2021, 07:18 AM   #7
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Check your fuses . There will be 1 or 2 labelled IGN. You should be able to find a manual online for the p30 chassis that will help in troubleshooting your problem.
1993 Tiffin Allegro Bay 32'
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