Fuel pump no power
 

Baja 232 w a 502 mag mpi.
I am getting 1.4 volts to pump. It’s not turning on. When I turn the key I don’t hear the beep along with pump turning on. I just put 2 brand new harnesses in it this weekend. My pump relay has 12v and the grey wire only has 1.4 I would think it would be much higher. Pump turns on if I hook it straight to 12v. Also not sure what these wires are for. I didn’t have them on my old harness.
https://cimg9.ibsrv.net/gimg/www.off...851a06023.jpeg
https://cimg1.ibsrv.net/gimg/www.off...fea66adee.jpeg
https://cimg6.ibsrv.net/gimg/www.off...94dd91ef2.jpeg

Motor serial number?

502 Mag MPI HJ 1996–2001, 6HJ

is there a grey cap on a plug with 3 fuses inside one is for the fuel pump ? if this an OE wiring harness

Yes grey plug has a cap

1996 to 2001 goes across 2 manuals, not a lot of help

The single wire Blue/Tan (if it is tan) would be for transmission over temp (you don't have)

2 prong connectors
Unknown because unable to find anything in diagrams using those colors at rear of motor

Note fuses 15, 16 and 17
The fuel pump has a ground and Gray going to power up when relay energizes.

Ignition ON, supplies power to MPR. The MPR contact gets power from the engine circuit breaker thru a fuse and Red wire. The MPR is energized via the engine harness to EFI harness thru a pink wire

MPR supplies power to ECM and fuel pump relay contact. FPR is energized by the ECM thru the Green/White wire

Since your not getting a beep, then the beeper may not be connected and/or your not getting power to the ECM


https://cimg4.ibsrv.net/gimg/www.off...2e0830b666.jpg

Wires are the same but would probably have all 3 fuses under one cap 13

https://cimg3.ibsrv.net/gimg/www.off...580f20d270.jpg

Has all three fuses under box. Relay is getting 12v through pink wire. Grey wire is only getting 1.4v. What is MPR?

Main Power Relay

How do I check that?

My pump relay is getting 12v but the grey power wire to the pump is only get 1.4v. Would not having power to ecm cause the pump to not have 12v?

Should have 12V on the Red wire full time, key ON or OFF
Should have 12V on Pink wire when key is ON

The Red wire goes to the FP relay then changes to Pink/Black after fuse to the relay and supply power to one side the relay main contact (30). One side of the coil is grounded (85), so when the Green/White wire gets 12V (86) from the ECM (J1 connector) it pulls the contact closed and passes 12V (thru Pink/Black wire) to the gray wire (87). Find out if your getting 12V from the ECM on the Green/White

If it is closing then maybe there is no power to the Pink/Black wire


https://cimg7.ibsrv.net/gimg/www.off...701272e841.jpg

That’s some great information. I plan on checking those things tomorrow and I will follow up on here. Thanks for everyone’s help so far

That tells me that the relay is bad. Probably a corroded contact. Either that or the grey wire is almost open somewhere. Is there another relay of the same part number that you can swap it with ? Where are you measuring the 1.4 volts ?

I am assuming that the relay is clicking ?

No corrosion both harnesses are brand new out of a box. The power to pump (grey) getting 1.4v

That’s exactly what I was thinking, or the 12v supply to the relay has a bad circuit and shows 12v until a load is intruduced(fuel pump) and then drops out. Only takes one strand to show 12v on a DVOM but takes a lot more to carry amps.

The 1.4V could just be the meter floating, but relay could be bad.

Unless the motor is running the FP relay will only turn ON for a couple seconds, then back OFF

Put meter on the Green/White at the relay. If there is no power applied from the ECM then the ECM is either not being turned ON (no beep) or ECM is bad, bad connection to ECM, something disconnected

The MPR and FP relay are the same and can be swapped

Is the relay "clicking" ?

Yes I do hear a clicking noise. I will check the ecm power and I have extra relays I can switch out. Thanks for help

If you hear the relay "clicking" then most likely the power from the ecm is fine. I would just swap the relay with another and try it. Quick and simple test.

There is a fuel pump driver in the ECM, many have failed,.....but if its activating the relay it sounds ok ??....swap the relay from the other harness and see if thers a difference

I did also swap ecm as well same reaction. The clicking noise couldn’t be something else I hear right? I will swap relays and check the power to ecm tomorrow check back in the evening I will have some answers.

So what I found is the MP green/white has 12v.
I swapped out FPR and still same thing just clicking. I checked to see if the FPR pink wire has power when key is off it does not. I checked to see if red wire has power with key off it does not. I did see I had this module on my original harness in last pic. Is it possible with the new harness I have the wrong ECM? I added both pics of the relays and my ECU.

https://cimg0.ibsrv.net/gimg/www.off...8a2f9fd79.jpeg
https://cimg1.ibsrv.net/gimg/www.off...24c882a77.jpeg
https://cimg3.ibsrv.net/gimg/www.off...1fcf04a94.jpeg
https://cimg4.ibsrv.net/gimg/www.off...213e7935d.jpeg

If MP means Main power then the Green wire should not have 12V on it full time, and the MPR does not have a Grn/Wht wire going to it.

Next both the MPR and FPR should have one black wire on each which goes to ground, but I don't see a black wire

With both the Red and the Pink not having power when key is OFF I'm not sure what you have

What was the part number that was ordered for both engine and MPI harness?

84-861162T1 is the main and I bought also the sister harness with the boat power plug.
The green/white wire only had 12v while key was on. Yes I noticed no ground on the FPR. I checked the ground that goes to the pump and used a ground on the meter and it was good. Still the grey wire to pump no 12v

Not 100% but do think you have the wrong EFI harness.
There are 2 part numbers found for Gen VI, one appears to be for MEFI-1 and P/N 84-861162T1 shows MEFI-1 and 84-860226A2 which does shows less uses (guess MEFI 3, but could also be for earlier MEFI 1 or 2)

Right now from your testing we know that the wiring is not correct or something is miss-wired

The MEFI-1 has grounds for both MPR and FPR, but the MEFI-3 uses ECM grounding to turn ON the FPR. Seeing only pink, Green and Red wires on the FPR I would bet your harness is for a MEFI 3

So would I have the wrong ECU? Damn so what can I do now? The reason I went through all this I got a complete engine from someone on here and things where so jacked up I’ve been fixing things for years. Also man really I appreciate all the help I really do.

If you were closer I would come over and have a look, but ... I'm not sure what you have, but from the wiring I'm seeing, I think you need MEFI 3 ECM to use the harness.

BIG NOTE HERE
That said, with enough time, I do think the harness can be modified to use the MEFI 1. Have not fully reviewed point to point, but changing a few wires should be able to get it changed over. This would take much more time for review for me, I've not looked into this before

BTW
Do the connectors connect without pins being bent or moved on the ECM?

engine serial number if this is a stock app and whats the calibration checksum letter and numbers ? I can match that up to which engines used that ECM

Hey BUP, can you advise which harness P/N is used for which ECM?

I don’t think the pins are being bent but I have not checked. Everything seems to plug in normally. What did you think about the module on the old harness? The original motor was a 454. What do you think is the best solution?

I have 2 MEFI 1 harnesses and no 3's other then what's installed on my boat. Always thought the connectors were different but they may be the same just at different angles.

The module is a knock sensor and is normal but didn't pay a lot of attention to it with current issues.

If it was mine and I spent this much to get it working I would try to change the wiring to make it work. I'm just talking out loud and have not had time to sleep on it and see if there were other options. A guy who I'm thinking might know is Articfriends

For the latest OEM cal using MEFI 1 was 10/ 2 / 1996 and cal checksum was 8E58. So what does your ecm say for that cal checksum when scanned ? Also what fuel injectors do u have installed ? Also the engine serial number will show what is needed for wiring harness and what fuel injectors needs to be installed and the manu date for the engine and so on. .

If I recall the MEFI 3 ecm and that calibration for the 502 came out 5 / 1998.

Not sure what injectors I have. Where is the serial number on block? When the guy put this motor together he did have to flash ecm that’s how I ended up with 2 ECMs. I still have the original harness I can take pictures when I get off work today. I don’t mind re wiring but I would have to have some basically tell me what goes where. Is there anything I can take pictures of to help out please let me know. Thanks for the helps guys.

If the serial number is not above the starter on a plate then its not there. The FPR can be rewired after knowing fully what is going on, but there are some other wires in the 1 going to pins that don't attach in the 3. The Grn/Wht should only come ON with 12V for about 2 seconds then back OFF. If it does that then it can be changed.

That said, the 1 has a few Orange wires (power from MPR) feeding different pins on the J2 side, but the 3 has only one feed (not shown)

Really need to know which harness part number was used with which ECM


https://cimg6.ibsrv.net/gimg/www.off...54437cbf1a.jpg

These are pics of my old harness. The new harness from what I was told is part# 84-861162T1
My injectors are the green 42s
https://cimg8.ibsrv.net/gimg/www.off...98bcc1beb.jpeg
https://cimg9.ibsrv.net/gimg/www.off...f4732156a.jpeg
https://cimg4.ibsrv.net/gimg/www.off...52d305b1d.jpeg
https://cimg7.ibsrv.net/gimg/www.off...184e5995d.jpeg

This is what I would expect to see with a MEFI 1
The FPR has a Black wire which goes to ground


https://cimg8.ibsrv.net/gimg/www.off...d3cc29326d.jpg

Went out to the shop and pulled MEFI 1 harness off the shelf and both of mine looks like your old one. I do believe you have a MEFI 3 harness installed on the motor. Would still be good if we could get a verification of part number

Also my original harness had electronic spark control that what that module I had a picture of. So I am probably not getting any spark either.

If I bought a MEFI 3 ECU for a 454/502 would that solve my problems?

MEFI 1 and 2 used an external spark knock control, the MEFI 3 and 4 the module became part of the ECM

Maybe, if you actually have a 3 harness then you need a 3 ECM to use it, otherwise you need a 1 harness to work with current ECM

Nothing is 100% right now