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Old 02-23-2019, 07:45 PM   #15
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Another Mike,

I had an 88 with 354. GMC added an elec gas pump because of vapor locking when towing and after about 6 hours in 70 + weather.

Glad you located the problem with damaged wire and got it fixed.

GM wouldn't auth removal of manual pump as it started engine and elec kicked in afterwards. I added a spacer on carb and heat deflector on exhaust but no luck.

Hope yours' goes better - Richard
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Old 02-24-2019, 09:13 PM   #16
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Quote:
Originally Posted by THOMAS10 View Post
HI ANOTHER MIKE just figured out to get back to your reply for me, thanks!! can you give me the info on that relay you said is available but it costs $80/$90 ?? would rely like to put that in rather the mod. the harness!! thank you so much! OH!!! i just got on this forum, so i dont have a clue what you meant by i wasnt the auther or something sorry! god bless THOMAS10
The GM part number is 15528707 but it is no longer available from any GM stealership I've talked to. I was mistaken that it was.

If you google that part number you will find an interesting thread on the Winnebago group about why those relays fail. They ARE repairable.

And supposedly they can be replaced with an AC-Delco 212-298 (if you can find one) but since I have a working electric pump I have NOT verified that (I've not needed to).

I have three chassis wiring diagrams... one for early carbureted engines that had the electric pump driven by the ignition switch, a later carbureted one that had the timer relay and oil pressure sensing switch, and a fuel injected engine diagram that used the timer relay and oil pressure sensing switch. The carbureted engines used a pump rated at around 3 to 4 psi, the fuel injected engines used a pump that would develop about 9psi.

One wiring diagram shows that the oil pressure sender (for the gauge) and the oil pressure switch (for the fuel pump relay) as two separate devices, each with one terminal, where another diagram shows them as a single combined device (with two terminals).

The later system used the timer to prime the fuel injection system, and the oil pressure sensing switch to shut off the fuel pump if the engine died for any reason - like a traffic accident scenario that killed the engine but left the ignition key on... you wouldn't want the electric fuel pump feeding a vehicle fire.

The timed fuel pressure relay is the expensive part and also hard if not impossible to find. The oil pressure switch is easy.

If you are wiling to wire your pump to run off the ignition switched +12 volt line from the battery, and change your behavior to turn the ignition key on and let the pump run for 10 seconds or so, then turn the key to start the engine then you don't need the timer relay. That's what I did - but I put a common cheap 12 volt relay in line to limit the current flow through the ignition switch and the oil pressure switch.

Below are diagrams that may help.

There is also a way to wire it using an oil pressure switch that has only one terminal (i.e. it switches to ground when oil pressure exists).
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Old 02-25-2019, 10:01 PM   #17
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"LAZARUS" I finaly got to the info you sent me ! thanks ,had some of it! I noticed alot of other posts under this THRED! about what im working on,from back in janury, i know where most of those parts actualy are hiding on the MH. , did you still need to know anything along the lines of what you wereasking earlyer?in the year? let me know,,
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Old 02-26-2019, 03:22 PM   #18
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"LAZARUS" I finaly got to the info you sent me ! thanks ,had some of it! I noticed alot of other posts under this THRED! about what im working on,from back in janury, i know where most of those parts actualy are hiding on the MH. , did you still need to know anything along the lines of what you wereasking earlyer?in the year? let me know,,
The Chevy manual says the timer relay is located inside the engine compartment on the drivers side. Mine isn't there. Any idea of where else it might be?
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Old 02-28-2019, 04:22 AM   #19
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The Chevy manual says the timer relay is located inside the engine compartment on the drivers side. Mine isn't there. Any idea of where else it might be?
OH YES GRASSHOPPER!! The first diagram you sent me is the one i think your asking about relay:15528707 ! thats the o.e.m. part, f.p. relay ! the one thats no longer avail. I went nuts trying to find BUT!! it is sorta. where they say , My RV is made by ELDORADO an encore model (22ft.) just is a knock off of a WINNE ! but not yerry good! the dash and dog house area are alot diifferant, and give terrible asces to the motor, impossible to get to that relay!! it was put in b-4 the motor!! anyways ,i just could not see it ,untill i took of the front left wheel ( drivers ) and ther is alot of sheet metal shieldig there ,like splash guards and such! there was i square hole in the sheet metal above the tirer, that is for access to the brake fluid ressivor, the cap is right on the other side and below the hole,!!!OK NOW! if you shine you lite straight into that acess hole you see more of motor and also thats where i saw the relay hanging from the pigtale,, iit was realy hard to get it unpluged , but when i opened it it had gotten water in it and was ruted totaly . once you can see or feel where it is ,you can go back under the rv and look up bto see it also!! ITT was there on mine but hard to find. I can tell you what i found and ordered to maybe replce it witout putting in a "CUDE" relay,,, its funny that on one of the other fourums they also had pages of posts back in 2014 about the same relay ,,i got to just read them all then go hunting on mine THANKS let me know!!
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Old 02-28-2019, 04:28 AM   #20
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The Chevy manual says the timer relay is located inside the engine compartment on the drivers side. Mine isn't there. Any idea of where else it might be?
OH ALSO !! I did find the oil presur. devices that ,goes to gauge and the other turns on with oil prssur!! that one i could jump wiyh paper clip to make the system thimk there was oil presur. or the motor was running!!
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Old 02-28-2019, 04:50 AM   #21
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Same stuff with older boats.

What some did was install a switch at the dash for the electric fuel pump to prime the carb.

I personally would not install the electric pump connected to the key switch.

Rochester needs 4-7 psi no more no less, more you will overpower the float.

Make sure of the psi hook a gauge to it and be sure.You don't want fuel going down the intake washing your cylinder walls.

I had points in my 1986 boat engine.

Really desperate for relays and such go to a site that sells marine parts .

Great lakes skipper, might have what you need.

Below was my engine in my boat, just look up your year and hp.

Mercruiser (200 / 5.0l / Lx 260 / 5.7l 350 Mag Alpha / Bravo) Engine Components
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Old 02-28-2019, 09:14 PM   #22
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HI MR> BOATS!! after reading a ton of posts about this ,and a ton more at another vforum , i found out that when those manual switches are instaled its because they never found the OME fuel pump relay!! or couldnt find a new one!! and that the meccanical f.p. thats bolted to the motor,, doesnt blow out the diafram in the pump is bucause of the return lines for the gas back to the tank!! i seperated the main fuel suply line going to the carb and stuck it in a 2 gal. of gas can , and ran the motor that way for a few minutes, but the motor sucked up that whole can of gas in just a few minutes. because it was pumping way more than the motor could use ,the rest went all the way back to the tank!!!
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Old 03-01-2019, 04:55 AM   #23
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Hi THOMAS10 ...

Chief Alen here, pleasure to meet you !

Allow me to educate you on the reasons and law of the seas.

How it is supposed to work in a marine boat engine is a little different then a MH.

With a marine boat engine that has a manual fuel pump there is 2 lines to the carb the main line and a line that hooks to the bottom of the pump, if the diaphragm goes then the fuel is pumped back to the carb .

Why one who doesn't know might ask ?

Because a reasonable and prudent person would not want fuel accumulating in the bilge of a running motor, bad things can happen, real bad things .

So fuel gets pumped back to the carb.

Some people might have redirected that second line back to the onboard fuel tank.

However that would lead a person to plug a marine carb return line .

Some people trying to save a few dollars would replace a marine carb with a auto carb hence no return line hole in the carb.

Back to the question put up by the original poster the reason for my previous post, needing a hard to find NLA part for a MH engine, and i believe i gave good info.
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Old 03-01-2019, 02:12 PM   #24
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Thomas 10, Just a little info about that pressure switch that is tied with the oil pressure gauge sending unit. My pressure switch blew out 1000 miles away from home. i lost 6 out of the 7.5 quarts of oil before I got the engine shut down. In trying to fix it I broke the "T"going to the engine trying to get the switch off. I managed to put a bolt into the opening where the brass "T" broke off. I had no oil pressure gauge and I did not jump the electric fuel. I was able to limp home on just the mechanical fuel pump.
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Old 03-01-2019, 08:09 PM   #25
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Thomas 10, Just a little info about that pressure switch that is tied with the oil pressure gauge sending unit. My pressure switch blew out 1000 miles away from home. i lost 6 out of the 7.5 quarts of oil before I got the engine shut down. In trying to fix it I broke the "T"going to the engine trying to get the switch off. I managed to put a bolt into the opening where the brass "T" broke off. I had no oil pressure gauge and I did not jump the electric fuel. I was able to limp home on just the mechanical fuel pump.
THE way you discribe it is just the way mines set up!there is also another device or sensor or something right above the frame crossrail near that oil switch ?? has one wier in it going into something like the breake line cluster?? I still have to back under and realy identify it ! the wier came down with those oil wiers from above !! mines on a T also but protected by the frame!
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Old 03-03-2019, 01:41 PM   #26
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Thomas, I would love to look at my setup to get an idea about that wire. but it's 30 degrees and snowing. Now if you want to wait till April I'll be more that happy to look at this . i can only think there might be two options, one it could be the switch to turn on the electric fans or maybe the sending unit for the water temperature.
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Old 03-03-2019, 02:44 PM   #27
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BA-in-mich, no!no! dont go out!! its 75* here in Tucson, You mentioned the fan relat, on my 1986 p30 454, its on the radiator suport ,to the left of it by the batt. silonoid, the # is 14101029, it looks exactly like the f.p. relay (15528707) inside and out, but wont replace the f.p.relay,tried it !,that fan relay is also NOT avail. , I did find 2 new relays on internet that look exactly like the OEMs same 5 pin pigtail and all, I tried them but no luck,!! BUT looking at the diagrahm for both relays, i think i just need to switch around the order of the rv wiers as they plug into the newer relays ( the 12345 wiers) i might be abel to show my diagrams to Chief Alen or Another Mike for a idea how to rearange the pins,, I have no savy,when it comes to relays ,, hope it gets warm soon!!
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Old 03-04-2019, 01:57 PM   #28
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There is a switch on the engine that grounds out once the temperature reaches a certain point. What I found is that a 12 volt light tester on the ground side of the relay will turn on the fans. The light bulb is enough resistance that will cause the relay to trigger on. I wound up putting switches in for each fan relay so I can turn them on anytime i need to.
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