Where's the Chevy P30 fuel pump relay?

Froggy1936 · January 18, 2014, 07:34 PM

Supplying battery power (fused) to the tan/white wire will run fuel pump irreagardless of anything else ( if wire from relay to pump is good) Run it thru a switch if you want the pump to shut off You can also incorporate a pilot lamp to show pump is on . Frank After following caution These instructions do not care about relay type The relay can be thrown away . But to use pump it would have to be turned on >

DaveVA78Chieftain · January 18, 2014, 09:48 PM

All stop froggy!!!!!
That is the wrong relay

You want one wired/marked like this:

For the one you are using, there is no normally closed (NC) pin so when you turn key on both NC and NO (normally open) pins are shorted together.

Dave

Note:
You have bottom right but need top center:

ClydesdaleKevin · January 18, 2014, 10:32 PM

Yep...I figured as much while I was pouring over the diagrams, and the differences between a standard headlight 5 pin relay, and the one I found in my drawer.

Turns out the one in the drawer was the original that was under the dash of the RV...and the one I installed, not knowing any better, was a standard relay.

I switched them out, and still no power to the fuel pump.

So I figured, hey...tan/white is direct to the fuel pump, and pink is hot when the ignition is on, right? So I reconfigured the wiring so that my toggle went to the tan/white and the pink.

Started right up, but still no juice to the pump!

Turned it off, and hit the toggle with the ignition key in the on position. Toggle lit up, but no juice to the pump.

Then I tried to restart it, and while the engine was turning over, it wouldn't start!

what in the world?

I sprayed electrical parts cleaner into the carb, and she started right up, and stayed running as long as I was spraying, but as soon as I stopped spraying, the engine would die. I pulled the fuel line off the carb, and turned the engine over...no fuel flow AT ALL!!!

So apparently the mechanical fuel pump has decided to give up the ghost!

Might be that the mechanical pump was dead on the way here, and I was running on just the electric pump!

Anyhow, the electric pump isn't getting juice even with the proper relay, bypassing it still doesn't get it powered up, and now the mechanical fuel pump has pooped the bed!

At least I have a brand new mechanical pump waiting to be installed, still in the box and plastic. So that is the first thing I'll be doing tomorrow. I put it off this long because the old one was working, and in order to get to the mechanical fuel pump on our rig, you have to remove the Safe-T-Plus steering stabilizer...so I put it off. Can't put it off now! Gonna have to bite the bullet and put it in tomorrow. Even if the electric pump isn't running, the mechanical pump should still pump gas at idle. Not sure if the converse is true though...not sure an electric pump will push past a broken mechanical pump.

In any event, as far as the electrical fuel pump goes, I have 2 spares in case this new one is shot...but I may very well have blown a fuse when I wired in the wrong relay earlier today. I'll check the fuses first before writing off the electric pump...and I'll test the pump with direct 12 volts.

So after figuring this all out, I decided to drive the Blazer into town 30+ miles away to see if I could get a new fuel pump relay in the original configuration. Went to Napa, Autozone, and O'Reilly's, and the Barth website spoke true...apparently the GM relay 15528707 is obsolete and no more! Unobtainium!!!

They couldn't even cross reference it, so I'm stuck with a rewire. I took the cover off the original, and you could see the black burns all over the circuit board.

So while I was there I picked up more zip ties and a 4 pin 30 amp relay just like I used when I redid the headlights last year.

My plan is to install the new mechanical pump, then look for a blown fuse to the electric pump. If its just a blown fuse and the pump becomes operational, we're all good to go. If its not a blown fuse, then I'll be running a brand new 10 gauge wire all the way back to the fuel pump, tie it into the relay, and have the relay triggered by the pink 12 volt ignition wire. Another 10 gauge wire will go right to battery with an inline fuse. I'm done playing around, and I'll rewire the damn thing just like I did the headlights!

Even if it is a blown fuse, I'm still going to run the 10 gauge wire I decided, but instead of tying it into the pink wire, I'll run it to the toggle switch on the dash, tie the toggle into the pink wire for a 12 volt source to trigger the relay, and another 10 gauge wire going to battery. That way, if a fuse blows or the electric fuel pump decides to get finicky again, I'll be able to hit the toggle and bypass everything, forcing it to run with direct 12 volt current.

I might just go ahead and rewire it to pink anyway, regardless of what I find out about fuses.

Gonna be a long knuckle busting day tomorrow! I'm sure there will be many curses as well...

Kev

circleD · January 18, 2014, 11:14 PM

Couldn't you use a jump box back at the electric pump before you run wire? Utilizing short scrap pieces of wire and see if it even works, kinda like a bench test minus the bench and comfortable seat

. Someone monitor the jump box and fuel, the other cranking the motor. This is just to narrow down the issue.

Froggy1936 · January 18, 2014, 11:25 PM

Kev it is past time for a fuel pressure gauge You are doing too much shooting in the dark. With your hot wire the pump shoud have run if all wireing is good .And switch is good electrical tester should verify or go direct without switch Pink is only hot with ign on Also better check for fuel in the oil sump if you suspect mechanical pump failure . Replaceing mechanical pump is not a waste of time if it is old A new one is better . Frank

ClydesdaleKevin · January 18, 2014, 11:27 PM

Not a bad idea, but I am now intimately familiar with the top of my gas tank and the electric fuel pump...lol! I have two spares, both take offs but I know the first one was running when I removed it. Not so sure about the second one, but it was less than 2 years old...and the one on the rig is only a month old! I'm going the whole nine yards this time, just like with the headlights. I'm sick of fixing the same thing over and over...time to fix it once and for all!

Dang that military truck is looking better and better! Nothing frail or fragile about those!

Kev

circleD · January 18, 2014, 11:31 PM

Good point Frank about the diaphragm it could be bad and letting fuel go by. THANKS FOR REMINDING ME OF ANOTHER PROJECT THAT NEEDS TO BE DONE D:oH!

ClydesdaleKevin · January 18, 2014, 11:33 PM

Thanks Frank. I'll check the oil to see if it smells like gas or has lost viscosity.

I have an inline fuel pressure gauge, but its plastic so I didn't want to leave it in place...I use it to test the system, then remove it.

When I went through all this crap last year and replaced the electric fuel pump and the carb with an Edelbrock, I used it to test the flow, and it was perfect.

Gotta be a fuse as far as the electric pump goes, or the wiring itself. Even direct there was no power to the pump. And the mechanical pump has definitely died. Cranking the engine, even with a dead electric pump, fuel should have poured out of the gas line when I took it off the carburetor. But nada, nothing. Not a drop.

I'm taking the hill tomorrow. All out, no holds barred, right up the hill with a primal scream, charging the enemy machine gun nest. Well, maybe not that dramatic, but I'm going to do it right, once and for all.

The headlights were a valuable lesson for me. Either dicker around with something peicemeal, or go for it all the way.

Kev

ClydesdaleKevin · January 19, 2014, 02:09 PM

Okay. So I wired it up to the correct relay, but using the diagram from the Barth site.

Turned the key to On, and hit the toggle. Nada. Checked the fuses, and the 20 amp fuse marked Choke was blown. Replaced it, hit the toggle, and the electric fuel pump ran long enough to start the engine, then blew the fuse again!

According to the wiring diagram Dave posted, the dark blue wire, which powers the relay, is in the same circuit as the choke, oil pressure switch, etc.

So, what am I doing wrong? How should I wire up this standard 5 pin relay so it powers the pump but doesn't blow the fuse?

I'm about to install the new mechanical pump, so I'll check back later this afternoon or this evening to see what you guys have to say.

Thanks!

Kev

Neil Carrick · January 19, 2014, 03:43 PM

Blowing the fuse indicates a dead short somewhere to ground. How did it quit the first go around with the old relay and wiring? Perhaps a short in the wiring from the electric pump up to where you are tying in now? Is the fuel pump new?
That's where I would start to look. Hm?

Froggy1936 · January 19, 2014, 07:35 PM

Well Kev First I dont think 20 A is high enough for a elec fuel pump . But you need to see if there is a short or an excessive draw Since i dont know if you still have the electric choke That wire may be lying loose near carb . Finding a short is not easy . Do you have any way of checking draw on curcuit ? This is the reason i reccomended a New separate curcuit for the fuel pump (run a new wire to the pump eliminate the old one ). Fused 30 A and switched with a New switch Then if you blow the fuse you know its the pump drawing too many amps . Frank

jkilbert · January 19, 2014, 08:03 PM

Aside from making sure you have adequate power make sure of a good ground. When I had my s-blazer I was going through fuel pumps like crazy. Turned out it was a bad ground causing the pump to pull too many amps then burn itself out.

ClydesdaleKevin · January 19, 2014, 08:13 PM

Oldrockandroller, called them and a few others that had them listed, and they are out of stock.

Thanks Frank. Could be the whole problem.

Since the relay is working to start and keep the engine running, I'm thinking of just forgetting about the 20 amp choke fuse, running a new wire for the choke off the hot wire of the distributor, and then installing the new 4 pin 30 amp relay specifically for the fuel pump. Still deciding if I want to run a lead from the pink wire to the proper pin on the relay to power the relay any time the ignition is on, or else do the same thing, but run it to the lighted toggle so I can see at a glance with a dummy light that the electric fuel pump is getting juice. In either event, I'm going to run a new 10 gauge wire right to the fuel pump, then to the 30 pin of the new relay. Then 10 gauge wire right to battery positive with a 30 amp inline fuse, and the other pin to ground with 10 gauge.

That will certainly solve the problem once and for all!

I had a pretty easy time with the mechanical fuel pump replacement today. The hardest part was cleaning off the old gasket, since its not exactly easy to get to. Removing the Safe-T-Plus steering stabilizer was easier than I thought it would be, so that gave me easy access to the pump from under the rig.

I used high temp RTV sealant on both sides of the new gasket...and on the pipe plug for the pushrod.

OMG the pushrod is WAY bigger than the one on the Dodge 413 we had in the Ark! I held it in place with wheel bearing grease when putting in the new pump.

Took all of 3 hours to do the job, and that was with lots of breaks.

WAY smoother and easier than I thought it would be!

No gas smell in the oil at all, so that's a good thing!

Tomorrow is wiring day, so if any of you have any better ideas than my direct wire through a relay idea, let me know before tomorrow morning...lol!

Thanks again everyone!

Kev

ClydesdaleKevin · January 19, 2014, 08:22 PM

Thanks jkilbert! I'll double check the grounds at the pump while I'm at it, but they were pretty solid when I recently checked it.

The pump was running briefly before the fuse blew, so I know it works...and running the new 10 gauge power wires should eliminate any electrical problems in the mix.

Only thing in the diagram that has me confused is that the blue wire, the circuit that keeps blowing, goes to the oil pressure switch as well...which I could care less about...and it says "ignition fused"...as well as the choke. The pink wire comes from ignition though. So I'm guessing this has something to do with the timer of the original relay? It starts and runs even with the choke fuse blown...cuts out because the electric fuel pump dies, but will run on electrical parts cleaner as long as I keep spraying it in the carb...lol!

Things are coming together. I got the mechanical side of the fuel delivery done today...tomorrow, its the electrical!

Let me know if you guys see something I'm missing!

Kev

DaveVA78Chieftain · January 19, 2014, 09:05 PM

Circuit description (Barth version):
1. When you place key to RUN prior to starting, no voltage to relay coil because oil pressure safety switch is not made yet. You can use the PRIME switch to pressurize the line prior to start.
2. When you go on to START, power is provided to fuel pump over NC (87A) contact to pin 30.
3. Once engine starts, oil pressure safety switch closes and allows power to relay coil blue wire (pin 85) from ignition run switch. When you release key from START to RUN, power stays applied to relay coil as long as A) engine is running (oil pressure safety switch closed) and B) ignition switch is in RUN. With coil energized, power for fuel pump is provided by pink wire to NO (pin 87) to pin 30.
4. If you are in an accident and the engine stops running, the oil pressure switch opens up shutting off the fuel pump. That is the safety part of the oil pressure switch

There is most 2 oil pressure switches installed. The small one (2" long and 3/4" dia) with 3 terminals is used for the idiot light and fuel cutoff switch. The larger "can" type (like shown in your other oil pressure switch posts for you toad) is used for an oil pressure gauge.

In original design:
Power to fuel pump when key in START is provided buy purple wire from starter solinoid
Power to fuel pump when key in Run is provided buy Pink wire from ignition switch

Choke fuse is only used for relay coil and choke (not pump power). The choke fuse would be a ignition switched circuit though. These ciruits should be low amperage. Nothing like the high fuel pump current.

Barth circuit:
Power to fuel pump when key in START is provided buy purple wire from starter solinoid (again pin 87A to 30)
Power to fuel pump when key in Run is provided buy Pink wire from ignition switch (87 to 30)

Either they retained the original circuit OR they moved the input to the oil pressure switch from the choke fuse to the ignition switch. Not clear from their drawing.

Dave

ClydesdaleKevin · January 19, 2014, 09:47 PM

Thanks Dave! That clears up a lot, but doesn't explain the fuse blowing, which I still haven't figured out.

Regardless, I'm going to run new wires via the new relay. Leaning towards the toggle switch which is lighted...if the fuse blows, the LED goes out, and I know its not running...lol! Light on, electric fuel pump running...no brainer!

That's tomorrow project! Gonna rewire the choke to the ignition positive on the distributor, and the relay to the lighted toggle most likely. That way I can prime it before starting, and then when started I know the pump is ON!

Kev

ClydesdaleKevin · January 20, 2014, 10:45 AM

Today is the big day when I get the darn electrical fuel pump working on its own circuit through its own relay.

Since I won't have the oil pressure safety switch in the circuit anymore, I wouldn't necessarily recommend the way I'm going to do this to others, but in a pinch, if you own a P30 chassis motorhome and the fuel pump relay dies, hopefully someone can glean some useful info from my fiasco in learning how to make other relays work.

I'll let you all know how it turns out this afternoon.

Kev

ClydesdaleKevin · January 20, 2014, 12:43 PM

So this is the exact relay I'll be using, a Novita RL44 40 amp unit:

I decided to skip the toggle switch, since it will light up no matter what if there is 12 volts going to it.

Instead I'm going to keep it simple.

The pink wire on the existing relay is 12 volts positive when the key is turned on. I'm going to splice into this wire with 2 leads. One will go to the electric choke, and the other will go to pin 86 on the new relay...that will energize the relay whenever the key is turned on...it will self prime without a toggle.

Right from battery, I'll be running a 10 gauge wire to pin 30 with an inline 30 amp fuse.

Pin 85 is ground, so I'll run a 10 gauge wire from there right to a good ground in the engine compartment.

Pin 87 is power out...I'll run a 10 gauge wire from this pin, all the way back to the electric fuel pump.

As long as the pump is still good, this should work out nicely!

Kev

Rickf1985 · January 20, 2014, 06:24 PM

I have a question. Nobody here has brought up why you have to prime it. This is a carburetor, not fuel injection. The carburetor bowl will have more than enough gas in it to start the vehicle and get the oil pressure up to the point that the electric pump kicks in. BUT, Even if the carburetor was dry (another problem that should not happen) you have the mechanical fuel pump which will draw at least 10" of vacuum, more than enough to pull gas from the tank and fill the carb. Kevin, I don't think you need 10 guage wire and a 30 amp circuit for a fuel pump. I have not seen your pump but I have run some pretty serious race pumps and they didn't pull 20 amps let alone 30. You do not want to oversize the fuze on the circuit, that can be dangerous. It is supposed to blow before something goes up in flames and to blow a 30 amp fuse is a serious short. You can run the 10 gauge wire but size your fuse according to the draw of the pump, you want the fuse to go before the magic smoke gets out of the pump. I have heard that the magic smoke and the gas genie do not get along well. W% It seems like a lot of your testing is "turn it on and see what happens" testing. That is not good and can get real exiting. You really need to invest in a digital meter and a test light. I have been watching this carefully because I have the same issues but in addition I have the regulator leaking back next to the tank and I can't get to it without dropping the tank.

Froggy1936 · January 20, 2014, 07:34 PM

Hi Kev Looking at amp draw for fuel pumps most are rated @ 20 A Draw so a minimum fuse would be a 25 A . .I dont think 30 A is too much . Also since GM only added these electric pumps for occasional Vapor lock your veh should run ok on just the mechanical pump If all fuel lines and filters are clear . Did you try to to see how much fuel is being pumped by the mechanical pump? Should be at least 1 Gal a min with a cold syestem . If not you have a plugged syestem or a leak drawing air Frank

gary19734 · January 20, 2014, 08:15 PM

As far as the choke wire goes if it goes thru what appears to be a oil switch this is actually an oil temperature switch witch controls the electric choke when mine went bad it blew the fuse and the choke light stayed on in the dash had to search a marine catalog at pepboys to find a new one hope this clarifies something Gary By the way theres 2 switches on mine the single wire works the gauge the two wire is the one that works off of oil temp for the choke

ClydesdaleKevin · January 20, 2014, 08:22 PM

Once again in the words of Stewie from Family Guy...VICTORY IS MINE!!!!!

There is a reason I don't play the lottery. There are 3 wires going to the fuel pump, and one is obviously a ground. So that leaves 2. 50/50 shot, right? One is 12 volts to the pump, the other is to the fuel gauge.

They look the same and are the same color. I snipped one, and turned the key...fuel gauge pinned. Yep! Not a lottery player! 50% chance of winning, and I still lost...lol! I hooked that wire back up, and then clipped the other wire and taped it off.

I ran fresh 10 gauge wire to the pump. I sacrificed my oldest 10 gauge extension cord to come up with the wire in the middle of the desert.

I tied it into the other wire of course, ran it up high along the frame rail with lots of zip ties, and right to the engine compartment.

To make sure the pump still worked, I had Patti stand near the tank and put the new wire to battery hot...BINGO!!! Pump running!

Then it was time to install the new relay. Found a good place to screw it down, added all the spade terminals, and wired everything in.

I didn't have a fuse holder, so used spade terminals right to a 30 amp fuse inline with the wire to the pump.

System test! Chassis power on, no juice to the pump. Key on...power to the pump!

Choke works great attached to the spliced lead.

It works!

Victory is mine!!!

Kev

Neil Carrick · January 20, 2014, 10:21 PM

Sounds great! Congratulations!

sometimes things DO work out.
Neil and Shelley

ClydesdaleKevin · January 21, 2014, 09:28 AM

That should totally eliminate the vapor lock from now on. I also backed the timing off a bit and set the idle accordingly, and then reset the idle power mixture screws according to Edlebrock specs.

Should run like a top again!

Kev

ClydesdaleKevin · January 22, 2014, 08:17 PM

Road test report: Fixed!!!

All power restored with no vapor lock. Drove it 35 miles with Patti following me in the Blazer, and no problems at all...runs perfect again!

Tomorrow we'll see how she performs pulling the Blazer. I have it all hooked up now, but we are pulled over for the night in a vacant lot in Safford, AZ. Only pulled it about 400 yards after hooking it up, but it seemed to pull it just fine.

We'll see what tomorrow brings! 100 miles to our next stop at Tonto National Forest, up some pretty steep climbs. That will be the real test.

Kev