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Fuel pump relay

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old55pete

Fuel pump relay

Been pouring over the EVTM's trying to figure out a problem with the fuel pump relay not energising and firing up the fuel pumps. What I am finding is that with the key on, I have three hots. One from the ECM( control power), one from the battrie ( controlled power ) and another one on pin 22 which is supposed to be a feed back to the ECM. I can jumper the controlled power and get the pumps to fire up. I am hoping that some one can correct me, but I thought that pin 22 was supposed to be a ground to pull in the relay and and put voltage through the relay to fire up the pumps.

Steve
86 Bronco, XLT, 5.0 EFI, EEC IV, AOD, IFS, limited slip front and rear, 3.08 gears, Tilt steering, factory AC

85lebaront2

Re: Fuel pump relay

Administrator

The way Ford set the system up, pin 22 is grounded upon initial key on, this is what gives you the short pump run when the key is turned on. When the EEC receives a crank signal (ignition pulse) it will turn the pump on to feed fuel to the cylinders.

Question, is the EEC power relay energizing? Without that none of it will work, circuit 361, red wire, is the feed from the EEC power relay to the system, pump control, ignition, injectors and all the solenoids. A very common problem on these is the system ground connector, C101, it is a 1/4" spade connector near the battery negative post and is very prone to corrosion. A bad ground will kill the system as far as running.

Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

old55pete

Re: Fuel pump relay

Bill, I have checked that ground as I noted that it was a part of that system also. I am thinking that I will replace it to know for fact that it is good. The thing I have going on is that it stays powered. So if I jumper it and get the pumps going, even through the start and run, it still stays a 12 volt. If I understand correctly, before you start it it is a momentry ground to get fuel pressure to start, when it is running it is supposed to be a ground after it gets oil pressure, yet it still has a 12 volt feed back. What am I missing here?

Steve
86 Bronco, XLT, 5.0 EFI, EEC IV, AOD, IFS, limited slip front and rear, 3.08 gears, Tilt steering, factory AC

old55pete

Re: Fuel pump relay

In reply to this post by 85lebaront2

I just cut out the plug on ground 101 by the battery and soldered the connection. I still have the same result.

Steve
86 Bronco, XLT, 5.0 EFI, EEC IV, AOD, IFS, limited slip front and rear, 3.08 gears, Tilt steering, factory AC

old55pete

Re: Fuel pump relay

In reply to this post by 85lebaront2

So, what would happen if I just cut out the old relay and put an equeal sized one from say NAPA and omited the return from the ECM pin 22 and made that wire a ground? That way I still have the control power from the ECM to turn on the relay with the key

Steve
86 Bronco, XLT, 5.0 EFI, EEC IV, AOD, IFS, limited slip front and rear, 3.08 gears, Tilt steering, factory AC

85lebaront2

Re: Fuel pump relay

Administrator

The reason it is done so the EEC controls it is safety, If the pumps run continuously and there is any problem they can empty the tank onto the ground, all over a hot engine or any of a number of scenarios.

FWIW, Ford and Chrysler both use the computer to turn on the fuel pump, both do the short "burst" at key on by grounding the relay coil. Chrysler's is called an Automatic Shut Down relay and it is wired into the EFI feed like the Ford Power Relay so it powers fuel pump, coil and injectors along with the O2 sensor heater. GM uses (at least the ones I have worked on) an oil pressure switch to control the fuel pump relay. I would find out why it isn't working correctly, could be a sign the EEC is on it's way out.

Bill AKA "LOBO" Profile

old55pete

Re: Fuel pump relay

In reply to this post by old55pete

I finally figured it out, the wires are shorted in the relay plug. I replaced the plug with one from NAPA and wired it correctly from the EVTM and now it works like it should. Fuel pumps come on for a few seconds then shuts off, start it and the fuel pumps run like they are supposed to.

Steve
86 Bronco, XLT, 5.0 EFI, EEC IV, AOD, IFS, limited slip front and rear, 3.08 gears, Tilt steering, factory AC

Gary Lewis

Re: Fuel pump relay

Administrator

Yippee!! Well done!

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

old55pete

Re: Fuel pump relay

And the plot thickins, it has now burnt up the new relay. I put in a relay test switch and powered the pumps, I could hear the pump in the tank come on but not the high pressure pump on the frame. Crawled under it and touched the hot wire in the pump and it was smoking hot. That pump was put in in may. I have a new one ordered from NAPA as that is where I got this one.

Steve
86 Bronco, XLT, 5.0 EFI, EEC IV, AOD, IFS, limited slip front and rear, 3.08 gears, Tilt steering, factory AC

Gary Lewis

Re: Fuel pump relay

Administrator

Yipes! The pump works, but is pulling way too much current? That sounds like a serious problem.

Have you checked to make sure that no one has bypassed the resistance in the pump circuit? I don't think that, by itself, would account for the hot wire. But it wouldn't help. (Sure seems strange that the Bronco has the resistor but the F-Series doesn't. Wonder why?)

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: Fuel pump relay

Administrator

The original pumps Ford used for the high pressure 1985-89 are Bosch ones, probably the same ones Mercedes used on their EFI vehicles in the 70s. My son had a 1986 F150 302 EFI truck, it had an aftermarket high pressure pump that worked but sounded like it was going to pieces. He scored a used one from a neighbor's totaled 1986 F150. When he sold the truck it was still going.

I would bite the bullet and try to find a Bosch pump.

Bill AKA "LOBO" Profile

old55pete

Re: Fuel pump relay

as the orignal pump was a Bosh and NAPA offered a Bosh, that was what I replaced it with. The one I am putting on today is a Bosh. After I got it out, I shook it and it sounded like a trash can full of rocks. I hooked it up streight to the battrie and it made a loud hum and if I hit it with plyers it would come on for a second or so, it got so hot that I couldent hold onto it. All of the gas that drained out of it is clear.

Steve
86 Bronco, XLT, 5.0 EFI, EEC IV, AOD, IFS, limited slip front and rear, 3.08 gears, Tilt steering, factory AC