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Discussion Starter · #1 ·
Need some help with my 1991 GTO
Fuel tank was filthy with stale fuel and the pump not working, flushed and cleaned the tank, refitted and installed a new 524 lph pump
ran it for a hour, took it for a drive the next day, drove for about 30 kms, then blew my clutch master cylinder ( found that I'd put a hole in the piston )
turned off while thinking how i was going to get home, went to start in gear fuel pump not working,
tilt tray home, thought might've been fuel pump relay, after arrival
worked out fuse number 12 was blowing when ignition turned on reds,
Did the ******* globe trick plugging in a globe into the fuse slot
unplugged fuel pump, turned on to reds each time, then mfi, fuel pump relay and when i unplugged coil the light went out
disconnected each coil pack one by one found the coil closest to the firewall triggering
ordered a new coil pack fitted today and exactly the same thing happens to the globe at fuse,
I removed the pump at one point and checked it was working okay out of tank, noticed the joining plug in tank had fuel around, there is a rubber grommet but still getting wet
Im not sure if matters,
It wasn't doing it before but with the coil pack unplugged, the MFI is repetitively clicking with the fuel pump plugged in,
disconnected the fuel pump, MFI clicks once on reds
I think maybe I'm dealing with 2 problems?
What do you think my chances are getting a new coil pack which is faulty
I might go swap coil packs around see if makes a difference
Clutch is all working now
Thank you for your help :)
 

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Need some help with my 1991 GTO
Fuel tank was filthy with stale fuel and the pump not working, flushed and cleaned the tank, refitted and installed a new 524 lph pump
ran it for a hour, took it for a drive the next day, drove for about 30 kms, then blew my clutch master cylinder ( found that I'd put a hole in the piston )
turned off while thinking how i was going to get home, went to start in gear fuel pump not working,
tilt tray home, thought might've been fuel pump relay, after arrival
worked out fuse number 12 was blowing when ignition turned on reds,
Did the *** globe trick plugging in a globe into the fuse slot
unplugged fuel pump, turned on to reds each time, then mfi, fuel pump relay and when i unplugged coil the light went out
disconnected each coil pack one by one found the coil closest to the firewall triggering
ordered a new coil pack fitted today and exactly the same thing happens to the globe at fuse,
I removed the pump at one point and checked it was working okay out of tank, noticed the joining plug in tank had fuel around, there is a rubber grommet but still getting wet
Im not sure if matters,
It wasn't doing it before but with the coil pack unplugged, the MFI is repetitively clicking with the fuel pump plugged in,
disconnected the fuel pump, MFI clicks once on reds
I think maybe I'm dealing with 2 problems?
What do you think my chances are getting a new coil pack which is faulty
I might go swap coil packs around see if makes a difference
Clutch is all working now
Thank you for your help :)
First, I will assume that a globe to an Aussie is a light bulb to an American. I will also assume that you attached the bulb across the two fuse contacts and no fuse in the circuit remaining. Your assumption is that a short exists if the bulb lights when fuse 12 would normally be powered. So, no short....no light! In this instance, this circuit, not necessarily true. Fuse 12 provides battery power to at least 5 different circuits that can be divided into three categories that get turned on only when the key is in a specific position....on/run/your"reds", start/crank....or back to run after the car starts/running and feeding a crank sensor and a cam sensor signal back to the ECU. You said the fuse blew every time the key was only turned to the on (reds) position. You were focused on the fuel pump being involved, but you changed several things each time between trials confusing matters. The fact that the fuse blew in only key on position rules out the fuel pump as a cause. Fuse 12 is powered when the key is turned to the on position feeding power to pin 62 of the ECU turning it on which activates the MFI power side sending voltage from a different fuse (ECI) to many sensors and the injectors. Key on also sends voltage to the ignition component category.....the PTU, the three ignition coils and a filtering condensor/capacitor for the ignition system. Fuse 12 also feeds two circuits that go through the fuel relay side of the MFI to power the fuel pump....but one is turned on only when the key is turned to crank position, and the second only after the car starts. So, forget the pump for now. The bulb will stay on even with no short in the ignition system(or all coils PTU and condensor disconnected) because the ECU is still powered on and connected to its expected ground. Your 1st generation ECU may be bad and shorting,but your bulb can't tell you. Unplug the two connectors to the PTU, the one connector feeding all three coils, and the connector to the condenser. Turn key to run and see if fuse 12 blows. If yes, ECU or wiring in circuits is shorted. If no, turn key off and plug in PTU only...key on. Then repeat one at a time with coil packs only, then condenser only....Don
 

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Discussion Starter · #3 ·
Hi Don,
your presumptions are correct,
As this all started with the clutch losing pedal wondering if it has done some damage under dash going to the floor crushed a wire?
It has an after market ecu and ignition system
after doing further tests today im further confused
found the centre coil was causing the bulb to light up took out centre coil, bulb doesn't light up now
When the fuel pump is plugged in now it is turning the MFI relay to a flasher relay continually clicking on off, removed pump tested out of tank wired just the pump no senders still same unplugged the pump and stops the mfi repetitively clicking, while it is clicking the bulb will flash on and off at the same time

Unplug the two connectors to the PTU, What is the PTU? power transfer unit? I'm not aware of this
the one connector feeding all three coils, and the connector to the condenser. Condensor? Air con condensor? or suppressor attached to coil pack bracket? i have an aftermarket ignition box under my coils

Turn key to run and see if fuse 12 blows. if it lights up it will blow so no need to put another fuse in it?

Thanks
 

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PTU is the Power Transistor Unit, what some manufacturers call the "igniter". It is mostly 3 larger transistors that drive the coils, and some circuitry for the tach.
The "Condenser" is, as you said, the suppressor attached to the coil pack.
Everything that mothsmoths said is dead on for a stock system but may, or may not, be true with your aftermarket system.
(The stock system does not prime the pump and only turns it on when cranking. Some aftermarket systems turn the pump on with the key "on" (reds).)
Can you tell us more about that? (brand and model)
He is 100% correct though that your test lamp (globe) can only tell you so much. It's indicating that there is current flowing, but not how much.
You could replace the lamp with an ammeter but most multi-meters can't handle the 10-15 amps this circuit draws and could be damaged in the attempt.
(Besides, I really couldn't tell you what a good coil draws vs a bad one even if you did have a number.. :unsure: )
What he's suggesting is to pick up a package of fuses and use them to gauge whether the draw is too much or not..

 

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Discussion Starter · #5 ·
Thanks for very helpful info Steve and Don
Have tested the MFI all working as per test
still it clicks if fuel pump connected

Ecu is Adaptronic select engine management e420d basic with a M & W Ignitions type ECU3 ill attach pics,

Cannot have fuel pump plugged in without the MFI relay clicking continuously on reds, bulb flashes (wouldn't blow fuse if inserted but i don't leave on long enough to do damage,)
Tried to crank doesn't make any difference, which is strange as i thought fuel pump only powered up while cranking or running
have unplugged condenser, coils and the ignition bulb goes out on Reds when i plug in coils it lights up bright will blow fuse straight away, disconnect centre coil and it doesn't light up, so Ive now got 2 blown coils as tried the last old one which was removed and it is still shorting lights up bulb brightly
I wondering if i unplug ecu if the mfi will click with the fuel pump plugged in?

I did read about the oxygen sensor shorting out blowing the fuse, but car is low and cant access atm


 

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Thanks for very helpful info Steve and Don
Have tested the MFI all working as per test
still it clicks if fuel pump connected

Ecu is Adaptronic select engine management e420d basic with a M & W Ignitions type ECU3 ill attach pics,

Cannot have fuel pump plugged in without the MFI relay clicking continuously on reds, bulb flashes (wouldn't blow fuse if inserted but i don't leave on long enough to do damage,)
Tried to crank doesn't make any difference, which is strange as i thought fuel pump only powered up while cranking or running
have unplugged condenser, coils and the ignition bulb goes out on Reds when i plug in coils it lights up bright will blow fuse straight away, disconnect centre coil and it doesn't light up, so Ive now got 2 blown coils as tried the last old one which was removed and it is still shorting lights up bulb brightly
I wondering if i unplug ecu if the mfi will click with the fuel pump plugged in?

I did read about the oxygen sensor shorting out blowing the fuse, but car is low and cant access atm


View attachment 308944 View attachment 308945
Didn't expect that info. Was the car used for drag racing? That computer is completely generic and is used for many car makes/models using different sensors, ignition systems, fuel injection systems, etc.,etc. Essentially every necessary wire has to be pulled from the old harness and put in the right spot on this computer. Then it interfaces on a laptop so each component can be turned on and programed individually based on what you want it to do based on parameters and input values. So, the previous owner made choices like whether the ECU would act as the power relay MFI/ECI directly or use use the stock MFI relay and how and when. Same with the fuel control relay half of the MFI being used or not or set up to activate a higher amperage aftermarket relay for a high output pump or turn on and program generic circuits within the ECU so it becomes the fuel controller bypassing the MFI. On top of all that, the stock PTU has been replaced with an aftermarket ignition controller/igniter wired in that creates higher voltage/amperage to charge the coils and then trigger the spark to the plugs.(CDI technology). Without knowing how and where all those wires are spliced and what connectors remain, its nearly impossible to help you. I've got some ideas to explain what may be happening, but need to know:
Are the coils still the stock ones and connected to the base metal plate with their wires uncut and connected to the stock square 4 pin connector just below the plate? Do you have a digital multi-meter and know how to use it? Do you also have an analog voltmeter(old needle type)? Is the fuel pump you just installed really 524lph and what make and model is it. Do you have the specs for it ...x/lph @ x [email protected] x amps ?? Was fuse 12 a 15amp fuse? Do you have the service manual for your car? When you say "fuel pump relay", are you talking about the one inside the gold MFI box?
 

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Discussion Starter · #7 ·
has a lot of money spent on it, supposedly 20k on motor rebuild but i think past owner got ripped off, Standard turbo's
( and some of timing order was incorrect reversed i can show you the position of leads were if you know why they would swap them? )
She has a Go fast Bits controller so you can tune yourself, i haven't played with that as yet as it was running fine
Ecu has been spliced in leaving all original wiring intact as far as i can see, a bit messy under there

Coils are standard using standard wiring and plate, have a cheap digital multimeter, might need instructions lol
Fuel pump is all okay, i have plugged in 2 different ones while out in the boot ( when cleaning tank made a block off plate for tank, no wires are crushed at tank i double checked that yesterday )
and mfi still clicks like a flasher relay sounds like its fighting with another relay, i did change 2 capacitors in air con controls before mfi started clicking on off repetitively, will be unplugging that this morning,
Fuse 12 was 15 amp
Bob recently sent me the manuals
Fuel pump relay under the air box, not the MFI relay have tested MFI and working correct
 

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Discussion Starter · #8 ·
air con controls unplugged hasn't changed
Unplugged and cleaned socket at the 5 pin fuel pump relay under air box, tested with fuel pump plugged in and mfi relay only clicked once likes its suppose to do
Have a i got 2 buggered 5 pin fuel pump relays? or is there a test i can perform, it seems like this relay is fighting with mfi relay
unplugged ecu and still same repetitive clicks from mfi and bulb lights up flashing in sync with mfi clicking as was doing..
unplugged the 2 pin resistor near the fuel pump relay and the mfi repetitive clicks but the bulb does not flash or light up? I'm not sure what that means or my next step
 

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air con controls unplugged hasn't changed
Unplugged and cleaned socket at the 5 pin fuel pump relay under air box, tested with fuel pump plugged in and mfi relay only clicked once likes its suppose to do
Have a i got 2 buggered 5 pin fuel pump relays? or is there a test i can perform, it seems like this relay is fighting with mfi relay
unplugged ecu and still same repetitive clicks from mfi and bulb lights up flashing in sync with mfi clicking as was doing..
unplugged the 2 pin resistor near the fuel pump relay and the mfi repetitive clicks but the bulb does not flash or light up? I'm not sure what that means or my next step
Need answers from you before I can go further.
1. Make/model of fuel pump and lph output.
2.What type of bulb are you using incandesant LED etc., and what wattage is it?
3.Use your voltmeter and test voltage of battery directly on battery posts.
4. You said you disconnected ECU and MFI clicked with key on. Did you disconnect all 6 connectors from the ECU ?
5. Is there any kind of anti-theft device on the car....even if its turned off or not used?
6.Make sure battery - cable is attached to engine at a bell housing bolt or starter mounting bolt.
7.Make sure two ground wires are present,clean, and tight going from battery - terminal directly to firewall attachment just below wiper motor.
8.Make sure there is a braided ground strap going from upper middle of firewall, across to plenum/accelerator cable bracket.
9. Put your hand on top of the MFI relay to be sure you feel it clicking when you hear it clicking.
10. Remove MFI from console wall and disconnect the connector. Look on back wire side of connector, inside the connector terminal 10 ports, and inside the MFI at all the pins. Look for burnt or melted wires or plastic or exposed bare copper on the wires or terminals that have been push back and not making good tight contacts on the pins.
11. In your engine pic I can't see where each spark plug wire ends up, but just seeing if each wire heads to the front or rear bank, there are mistakes. Going from the firewall to the front of the car, the order should be 1 4 2 5 3 6.
Don
 

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Discussion Starter · #10 ·
1. China 525lph Hellcat Walbro copy ( but i have a working walbro smaller pump i tested and the old smaller pump tested to do the same repetitive clicking while plugged in)
The 525LPH pump can flow anywhere from 15-120psi (the bypass valve is set higher than Walbro's previous fuel pumps, which were around 85psi). Final fuel pressure is determined by your fuel pressure regulator. Please note that this is an aftermarket fuel pump, and some modifications may be required to get it to fit. The overall size is very similar to Walbro's previous generation GSS340/GSS341/GSS342, however the base is slightly enlarged as shown in the pictures

I know where you are coming from that the pump might've drawn too much current and damaged something? ( i will be wiring up an add in relay soon to the pump and see if it stops the mfi repetitive clicking )

2. Standard 12 volt Blinker/parker bulb 21 watt

3.12.36 volts

4. I disconnected the whole ECU no plugs attached apart from vacuum line and yes MFI constantly clicking like a flasher relay
( Originally when i started to do testing it blew half a dozen 15 amp fuses as soon as you put on reds, with the globe in fuse 12 position it was not repeatedly clicking, initially only once on reds and again on crank whilst holding mfi so i could feel it ) not sure why it repetitively clicks now all the time on reds, im not leaving on reds for too long so to not do more damage

5.. it has an alarm and is working correctly like it has done for the past 7 years


6. all earths are in place and same as they have been since i bought it, no major work has been done on engine
although the exhaust was pulled out while cleaning the tank and repainted, there was a braided earth wire which had been on exhaust to body was broken and another terminal fitted and bolted back on bracket after repainting exhaust installing the Fuel tank
I'm wondering if a oxygen sensor is shorting?

7. All good
8,.All good

9. definitely clicking repetitively

10. all inspected and clean no burnt wires or loose connectors, all wires in perfect condition





11. "Currently" in pic was (2016) what the old firing order was before i swapped around to the stamps on coil bracket and it runs fine, 142536
i just mentioned that as the motor cost 20k to rebuild 7 years ago and they couldn't even put the timing correct,


Thanks for your help
 

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Discussion Starter · #11 ·
Okay Good news :p an added 4 pin relay temporarily at the fuel pump out of tank runs the pump and mfi doesn't click, I still have 1 coil taken off plate waiting on a new one to arrive
What other damage have i done?
 

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It is 3 in the morning here so I gotta go to bed. But, I wanted to just give you a few super quick facts since we have opposite sleep/wake times living 12 time zones apart. When you use a light bulb as a fuse, it regulates the maximum total current/amperage that is available for every component operating on any circuit branch beyond that point that is being powered through that 15 amp fuse/now bulb..The factory fuse #12 (15amp) circuit powering its original stock pump, igniter, ECU, coils, etc., had a total current draw probably close to 10-12 amps. Your high current aftermarket replacement igniter probably raised the current draw close to the 15amp blowing point of that fuse. The new pump you just installed by itself draws 20+ amps depending on demand. The stock wiring to the MFI, the MFI fuel relay contact points inside the MFI that turn the pump on/off and pass the current on to the fuel pump, the wiring after the MFI, the pump speed control relay and its resistor pack are not capable/designed to carry that much current. So, those components quickly get hot and melt/burn when powering your new pump. That ends when something is toasted and comes into contact with any metal chassis area or a melted wire melts into a neighboring ground wire causing the fuse to blow. Using that light bulb drastically complicates everything. Your bulb is 21 watts.....watts=ampsXvolts.... so 21watts/12.36volt= 1.7amps maximum leaving the bulb to power that entire circuit now. You are expecting the amount of electricity that it takes to turn just 1 turn signal bulb on and off to power your entire fuel pump system, ECU, and your entire high voltage/high current ignition system at the same time you may still have the shorted part that blew the 15 amp fuse still in place and still shorting out. Nothing will work as expected and your ECU and your igniter will keep turning on/off rapidly making MFI click rapidly as the bulb blinks. The logic/processor chips inside the digital electronics are designed to do this for fire safety and prevent their own destruction. Normally, when the igniter turns on it charges the coils. But now it instantly shuts back down which triggers the coils to discharge a spark.to the plugs. The rapid blinking/triggering on/off coils get super heated and become toast quickly as you saw. That also creates another new short to ground regardless if the pump circuit is unplugged. Thats why you don't use light bulbs as fuses.You may have also toasted your igniter's internal thyristors,charging capacitors, or transistors by now. The MFI is likely shorted inside now also. The two internal MFI relays click on when the ECU provides a ground to activate them. The fact that the MFI relays rapidly click even when the ECU is fully disconnected and not providing any ground path to turn them on/off is a bad sign. On the 91-93 MFI relays there are 2 extra pins (10 vs 8 after 93). One of those pins goes straight to ground-pin6 and could make the MFI click when the ECU is disconnected, but only if the fuse 12 input to the fuel side MFI internal relay has already melted/shorted and remains in that state. You need to use your multi-meter and go part by part. Your pump will need to be powered by the battery through bigger gauge wiring with a 20-25 amp fuse in-line (not fuse #12) and through a 30Amp relay. If the relay and wiring you just installed isn't rated for that current, it won't last long and is dangerous. Good luck....your buying my Fosters !!!!
 
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