93 Mm v6 4x4 has just given up on life

[BradMph]

Fuel, electrical, mechanical, if things get to be causing headaches you can always revert back to basics. If you had another computer you could try could be helpful. Repairing those boards is so touchy and what you see with eyes that may need repairing is all good and stuff, but what made it fail could be something entirely different.
Careful not to chase the problem with money either. This has happen before and I have done it, but when you find the problem you will probably kick yourself about it for not noticing it before the work began.


We have coated boards with a harder wax as well. Just like candle wax but not as soft as what a candle is made of. Kept moisture out and was a basic easy fix and you can remove it to make additional repairs.


Hey Jeff,
I was having issues like you may of been having. In my case I was using the stock in tank fuel pump when trying to keep a modded motor running. I finally located the problem which was the car thinking it was not firing up an engine from the false signals the computer was getting. So, computer would send a signal to the in tank fuel pump cutting power and shutting it off and the car died after it finished the fuel off in the lines. In tank pump is removed and 2nd return line also since it was not required on the build and bypass computer on new exterior fuel pump.

[Chargerx3]

I would go back through and double check everything. Make sure your fuel quality is good and that your tank is filled up enough. Also make sure timing marks are on, spark plugs are in good condition, adequate spark from the distributor, etc.

[Chyrio]

I went over the board with a magnifying glass and then sealed it with rustoleum leak-seal which seemed to do the job. Also could it be that the previous owner put copper plugs in it? I know the manual calls for nickel? Tonight i will check the timing and injectors and the pump if i can. I'll take pictures if i can!

[Chyrio]

I also i know it sat for a while because the battery was completely dead but i don't think it sat long enough for the fuel to go bad.

[Chyrio]

PROGRESS!!! Alright so i checked again to make sure the pump was working so i took a bucket and manually pumped some fuel out with the bypass and noticed the fuel looked like this
IMG_20160307_190427.jpg
So i drained most of it out and went down and filled up my 5 gallon fuel can with 90 octane and put some of that in there and bam! it stumbled and stumbled and tried to start then died. then i tried again and it stumbled and stumbled and then misfired and died. so onto a new issue but atleast i know that it will start sort of! sounds like timing to me what do you guys think?

[tink]

You don't necessarily have to get it to run to read codes sent out by the ECU/ECM, just putting the key in the 'on' position can (not promising 'will') do the trick. For using the paperclip method the engine is to be left OFF. I had went thru this on a '93 3000gt & was able to figure it out by reading the long & short bursts on the analog meter. See: http://web.archive.org/web/201212011...codes91-93.htm for basic idea instructions BUT you will need to find the pins & fault codes that match up w/the ECU you are working with. Highly suggest letting it tell you whats wrong if it will rather than chasing a likely combination of issues. Good luck

[Chyrio]

You don't necessarily have to get it to run to read codes sent out by the ECU/ECM, just putting the key in the 'on' position can (not promising 'will') do the trick. For using the paperclip method the engine is to be left OFF. I had went thru this on a '93 3000gt & was able to figure it out by reading the long & short bursts on the analog meter. See: http://web.archive.org/web/201212011...codes91-93.htm for basic idea instructions BUT you will need to find the pins & fault codes that match up w/the ECU you are working with. Highly suggest letting it tell you whats wrong if it will rather than chasing a likely combination of issues. Good luck

Thank you sir! this is awesome i was looking so hard for a chart that shows just this a couple days ago!! Now i just need to go buy a analog multi-meter. But i just ripped the front of the engine apart and checked the timing and it looks like everything is on point and the belt doesnt look to bad i suppose it has been done in the past 20k or so.
IMG_20160307_205203.jpgIMG_20160307_205235.jpgIMG_20160307_205251.jpg

[Chargerx3]

Great start. This has me wondering now that your fuel system is the culprit. I just got done with a similar not WA ting to start issue. Turned out that the last guy installed the new fuel pump wrong. I'm wondering if your fuel pump is on its way out. Also have you changed your fuel filter?

[Jeff V.]

You don't necessarily have to get it to run to read codes sent out by the ECU/ECM, just putting the key in the 'on' position can (not promising 'will') do the trick.

The ECU will show stored codes without the engine running, but it doesn't actually run the tests that set the codes, until the engine has been running for a period of time. Since he's unplugged the ECU, there won't be any codes stored from the previous run cycles.

It doesn't hurt to check, but I wouldn't get my hopes up that there will be any results.

[Chyrio]

Great start. This has me wondering now that your fuel system is the culprit. I just got done with a similar not WA ting to start issue. Turned out that the last guy installed the new fuel pump wrong. I'm wondering if your fuel pump is on its way out. Also have you changed your fuel filter?

well the fuel pump is running strong. i mean it pumped out that whole tub of bad fuel in like 3-4 minutes. the filter looks like it has been tampered with recently but it hasnt been on there long, its not even close to as dirty as the bottom of the truck. plus if it was not getting enough fuel why would it be misfiring? maybe they put the filter on wrong. my thoughts right now are 1. wrong spark plugs + possibly fouled spark plugs from me trying to start it so many times with the bad fuel. 2. distributor is on the wrong way and its firing on the exhaust stroke (had a toyota do the same thing when the distributor was reversed) possibly happened during troubleshooting on accident? 3. ecu could still be bad. but like everyone has been saying because i unplugged it to check i lost any codes. i am going to go pick up a analog multi-meter soon to double check.

[Chargerx3]

I like your new order of operations. Do that.

[Chyrio]

I cant seem to find nickel spark plugs (what the manual calls for) anywhere in town? what kind do you guys run?

[pennyman1]

NGK plugs - autozone has them - use platinum plugs, they will run smoother and last longer than nickel plugs

[Chyrio]

NGK plugs - autozone has them - use platinum plugs, they will run smoother and last longer than nickel plugs

I have actually never heard of nickel plugs, combined with the fact that no one seems to carry them I'm assuming they are not very popular. Looks like buying new plugs might solve my issue ha ha.

IMG_20160308_170152.jpg

[Chargerx3]

Yea those aren't the best looking. Platinum will do just fine.

[Chyrio]

plus whoever changed them only changed 4 of them??? so there where 2 NGK nickel OEM plugs and 4 Champion Copper plugs???

[Chyrio]

Ok, so changed the spark plugs and that didn't make any difference, climbed under the truck and noticed the fuel filter was in the wrong direction.... stupid people man... so i took it out and did my best to clean it out with some brake cleaner and blew some air threw it and it doesn't seem clogged. Put it back in in the correct orientation and with high hopes tried to start it and.... nope same issue. so far here is what i have checked:
Timing
Fuel
Fuel Pump
Fuel Filter
Spark Plugs
Camshaft Position Sensor
Replaced Capacitors on ECU
Cap and Rotor
Ignition Coil
Distributor is in the correct direction at TDC

What happens when i try to start it:
Press Clutch
Turn key
Immediately hear a relay click on the passenger side
Turn key to the Start position
Immediately hear the relay click again
Truck turns over several times
Stumbles
Stumbles
Dies

Only things i can think of that i have not checked:
Compression
Swapping ECU for a good one

Any other advice/ideas???

[mightymax37110]

Mine was doing the stumbling thing until I changed the MAF

[Chyrio]

Mine was doing the stumbling thing until I changed the MAF

but wouldn't, in that situation, unplugging the maf make it run right? because i tried that too...

[Chyrio]

Another note worth mentioning. If you try and try and try to start it, eventually (4 or 5) tried it will start to smell like bad exhaust. like not burning antifreeze or oil smell just like old musty engine exhaust smell. Also if you try it 4 or 5 times. around the 5th time, you will hear a POP noise from the engine bay, not from the exhaust.

[Chyrio]

I was thinking, when your looking at the distributor while the engine is at TDC. should the rotor be on its way past #1 or like it just started the spark? I made a picture showing what I'm saying, Red is where its currently touching the cap at TDC:

Untitled.png

[Chargerx3]

Which way is the distributors direction? It's either advanced or full retard. Pun intended.

[Chyrio]

Which way is the distributors direction? It's either advanced or full retard. Pun intended.

Well if your referring to the direction of the adjustment bolt for the distributor, i have it set smack dab in the middle right now.

[tink]

basics are fuel spark air. if you've already covered the fuel (tank to combustion chamber) and spark (battery to spark plug tip) , then air is left ... other than computer controls / wiring / and moving metal bits. advice to stick to the basic that remains: air. if the air flow in/out is decent enough, double check the fuel flow since it could be getting a good enough amount of air in AND out, but the air /fuel mixture is so far off balance that you're smelling smells to indicate that even if/when it runs for a few minutes it's set to be running way too rich. the pops could be air pressure build up escaping or could be mini explosions of doom ...

hard to guess so thinking best to stick to the basic air flow that should be happening, from intake to exhaust. vacuum tube got blockage or pinched off, banana in the tail pipe or what? i hate guessing. but if the exhaust smell isn't making OUT the tailpipe, where is it getting hung up or where is the air blockage that's making the smell so strong?

the last time I heard pops from the engine bay was after I ran the truck out of gas, and so all the sludge that was at the bottom of the tank got pulled into the line right before the fuel filter, gummed up the filter, hesitations and no power and stuttering and ... POP. 3x it popped limping on the way home. changed the filter, and filled up the tank & been keeping it over 1/4 full since then, lol.

when you pumped out all that fuel you didn't happen to empty the tank did you? just a thought. if your filter is semi-see through, i'd shine a flashlight behind it & look in & double check it for gunk if your tank got down to E in the process of checking the fuel pump.

tldr; either way: pop can = air /fuel mixture way off.

hope my random thoughts from limited experience helps in some way. I totally feel your frustration & surely you'll figure it out anyway

[Chyrio]

hard to guess so thinking best to stick to the basic air flow that should be happening, from intake to exhaust. vacuum tube got blockage or pinched off, banana in the tail pipe or what? i hate guessing. but if the exhaust smell isn't making OUT the tailpipe, where is it getting hung up or where is the air blockage that's making the smell so strong?

the last time I heard pops from the engine bay was after I ran the truck out of gas, and so all the sludge that was at the bottom of the tank got pulled into the line right before the fuel filter, gummed up the filter, hesitations and no power and stuttering and ... POP. 3x it popped limping on the way home. changed the filter, and filled up the tank & been keeping it over 1/4 full since then, lol.

when you pumped out all that fuel you didn't happen to empty the tank did you? just a thought. if your filter is semi-see through, i'd shine a flashlight behind it & look in & double check it for gunk if your tank got down to E in the process of checking the fuel pump.

tldr; either way: pop can = air /fuel mixture way off.

hope my random thoughts from limited experience helps in some way. I totally feel your frustration & surely you'll figure it out anyway

Ok so to answer some of your questions:
Yes i drained the tank to below E but fuel was flowing properly, their was a steady stream of fuel coming out of the pressure line.

Checked the fuel filter and there was gunk that came out of it especially since it was installed in the wrong direction. But i tried to clean it out with brake cleaner and blew air through it and it does not seem clogged.

And i have checked every vacuum line i could find as well as you're apart the intake and there was no noticeable blockage or damage. I have tried with the MAD plugged in and Unplugged. However i have not checked the TPS or throttle body for issues which i shall try tonight.

Thank you for your thoughts! Any advice is appreciated!