Hang on this one is going to be a little bit long!. So I have a 1989 Ford Mustang GT t5WC but the tranny and engine are out of a 92. It's pretty much stock besides a power typhoon intake,70mm throttle body, cold air intake, short tube headers to an h-pipe and flowmaster super 40s and an SCT Chip Tuner. Everything related to smog has been removed and I have never had a cel until now. In December of 2023 the fuel pump got clogged and I cleaned the sock, ran fantastically. My father had the car up until last week working on the subframe connectors (He just got to it now, has a lot of projects) Anyways as of lately I have a CEL with codes 15,67,85,84, and 95 however if I remove my tuning chip I get codes 67,81,82,85,84, and 95 so pretty much similar with some small differences. I have tried chasing it down, I unplugged the bap sensor it was worse, cleaned the MAF sensor and checked the wiring near there and they were fine. It comes on at idle sometimes and raises the idle or comes on pretty consistently when I'm driving under throttle most of the time it goes away when I let off completely. I can't figure out the root of the problem as before the fuel pump was cleaned I never had this problem until now. In the last week, it has come on more constantly and before it went on and off pretty frequently, it still stays on while I'm WOT. It seems to be robbing power because when it's off and I slam on it I can feel the car slow down a bit once the CEL comes on. Since December the only thing that has changed is it having subframe connectors and I don't believe any wiring got chewed by mice at least I'm confident in that under the hood but I could be wrong. Please reach out with any and all information. thank you!
89ripper
Founding Member
Hmmm.. so after screwing with fuel pump its acting funny? When my car is down on power, i usually look to fuel first. Whats your pressure set at? Did you happen to see what code 95 is?
I have no clue what any of the codes mean and I still have the stock fuel rail, however the fuel pump is a walbaro 255lph fuel pump so maybe to much psi? Also if I unplug the maf the car will not run at all even with giving it throttle it dies out, if this means anything?
89ripper
Founding Member
First check the code.
stangnet.com
code 95
Fuel pump secondary circuit pcm to ground, its the only code I have that isn't smog related. What is it? I am assuming its the fuel pump relay? Does it just need to be replaced? Engine has only been in the car a short while, could I have put a wire in the wrong place? this car has gone from...
stangnet.com
89ripper
Founding Member
Your other codes are smog related, code 15 has to do with your chip being unplugged. Code 67 has to do with the clutch circuit
I checked the fuel pump relay and that seems to have good power going to it, cant really find any more information on it.First check the code.
code 95
Fuel pump secondary circuit pcm to ground, its the only code I have that isn't smog related. What is it? I am assuming its the fuel pump relay? Does it just need to be replaced? Engine has only been in the car a short while, could I have put a wire in the wrong place? this car has gone from...
89ripper
Founding Member
Just the relay? Did the grounds and power wire to the pump look ok? Also what exactly clogged your pump? Still have the stock fuel pressure regulator?
I did look at that stuff and all looked okay and even ohmed it out and everything was making a solid connection. Don’t know what clogged the pump seemed to be debris like black gunk, fuel tank was completely clean and no rust. And yes sstill the stock regulator
89ripper
Founding Member
Ok. Provided all connections are tested and are good, got a pressure guage? Monitor fuel pressure at idle, and wot...see what its doing.
Code 19 according to the post may have just been a one time thing, but needed to make sure circuit was all good.
Code 19 according to the post may have just been a one time thing, but needed to make sure circuit was all good.
Clear all of the codes and go for a drive. Pull codes again and list them here.
No such animal unless your Fuel Pressure Regulator is malfunctioning. I run a 255L High Pressure pump at just over 14 volts from a regulator. I'm pushing a lot more fuel than you are through stock rails and a stock FPR.
This leads me back to your "chip". Does this chip contain a custom tune or a canned, off-the-shelf tune?
What size are your fuel injectors? What cam are you running? I see no reason so far, why you should be running a "chip".
After you have cleared current codes, run the car, and pulled new codes to post here you should then:
Clear all the codes, pull the "chip" run the car, and pull codes again.
If we determine the "chip" is bogus then it may cure some of your issues. If it actually carries a custom tune, then the pins on the chip and on the EEc should be cleaned with contact cleaner and the "chip" reinstalled.
89ripper
Founding Member
Im glad youre here people start talking "chips" im like
Its all over my head i thought it was some new tech that I dont know anything about not like my old 90s JET chip mistake
67 - A/C Fault -- Turn the A/C to the [OFF] position
81 and 82 - Air Diverter valve fault -- Smog stuff removed?
84 - EGR Control Valve Failure -- EGR Removed?
85 - Canister Purge -- Maybe yanked alongside the rest of the smog stuff?
95 - Fuel Pump Circuit Fault
I think we have a "Bingo". Something is up with your pump, fuel pump relay, or the wiring in-between.
81 and 82 - Air Diverter valve fault -- Smog stuff removed?
84 - EGR Control Valve Failure -- EGR Removed?
85 - Canister Purge -- Maybe yanked alongside the rest of the smog stuff?
95 - Fuel Pump Circuit Fault
I think we have a "Bingo". Something is up with your pump, fuel pump relay, or the wiring in-between.
In the 90's through the early 2000s and maybe even today, there were these Off-The-Shelf "Performance Chips" that you could buy right off the pages of a magazine. They did some "things". The short version is that they are complete and utter garbage.Im glad youre here people start talking "chips" im like
Its all over my head i thought it was some new tech that I dont know anything about not like my old 90s JET chip mistake
These however, should [not] be confused with actual "Tuner Chips" that contain custom tunes for a specific car and combo. When you buy a used Fox and it has a "chip", one of the first things you need to do is to determine which of the above, applies.
Since his combo is so mild, I am [guessing] that it's a Garbage "chip". (I have to roll my eyes every time I encounter or have to type the word, "chip"
because they are that effing good )
On a side note:
I am going to drop this here so that the OP (and anybody else) can save and/or print a copy: (It's nice to have a copy on your phone)
I am going to drop this here so that the OP (and anybody else) can save and/or print a copy: (It's nice to have a copy on your phone)
89ripper
Founding Member
This is helpful. An old book of mine had code 67 as "clutch switch circuit failure"
The A/C switch off makes more sense
Okay so did some digging, these codes are ones I have had prior back in like july of last year and never had a CEL on with any of that and figured out it was due to my maf even when it didnt have a code for it just remembered I put all my codes in my note app and just forgot about this. The chip holds custom tunes but it has been removed, and the codes with 81, and 82 are the ones that popped up and code 15 went away because thats the code when the tuning chip is plugged in. So ive had all these codes for over a year but never had the engine light on. Im going to check fuel pressure and for vacuum leaks and see if that brings me anywhere. The reason for the chip is because I had plans on upgrading cam and heads but still havent gotten to it, I have a tune thats custom to what I have done to it not what it doesnt have to it and the tune has never given me a problem but like I said it has been removed.
89ripper
Founding Member
Youve never disconnected battery since then? Reset computer, check again after a few drive cycles. I cant speak about your chip just a point to consider in the steps of diagnosing your car
Let me just start fresh. I have disconnected the battery several times, even replaced it since last year. The codes have always remained the same for whatever reason. The chip has been out of the ecm since I got the cel it was the first thing I checked and removed. So thats no longer causing a problem and I disconnected the battery after that and its still the same stuff. The CEL Used to only come on after it warmed up now its always on, if I unplug the mass air sensor it immediately shuts the car off. Don’t know if thats related.
Do you still have a code 95 for the Fuel Pump Circuit Fault?
If so, that needs to be addressed.
After that, we can talk about doing a [Base Idle Reset] procedure to get the IAC settled/eliminated from your current issues.
If so, that needs to be addressed.
After that, we can talk about doing a [Base Idle Reset] procedure to get the IAC settled/eliminated from your current issues.
89 Mustang Fuel Pump Circuit Fault
Based on the search results, here are key findings and recommendations:- The fuel pump circuit is monitored by the Engine Control Module (ECM) through pin #37, which is the power “secondary” circuit.
- A faulty fuel pump relay or grounding issue can cause the fuel pump to malfunction or not run at all.
- The fuel pump relay is located under the driver’s seat on 1989 Mustangs.
- Inspect the electrical wiring, as overheating and melted insulation can occur, potentially causing issues with the fuel pump circuit.
- Test the fuel pump relay by removing it from its socket and checking for resistance between the light blue/orange wire and ground using an ohmmeter. The reading should be more than 10 K Ohms or an infinite open circuit.
- Before replacing the fuel pump, ensure the inertia switch is set correctly and the fuel pump relay is functioning properly.
- If the fuel pump still won’t run, consider hot-wiring the pump by connecting pink/blk to orange/lt blue (verify wire colors match your vehicle) to confirm pump functionality.
- Verify the fuel pump relay is functioning correctly by checking voltage at the FP relay wire and both sides of the inertia switch.
- Test for spark at the coil, distributor, and #1 plug to rule out ignition system issues.
- Check for 12 volts at the ignition switch and EEC FPTP (Fuel Pump Trigger Pulse) to ensure proper power supply.
- Inspect the fuel pump wiring for signs of overheating or damage.
- If all tests pass, consider replacing the fuel pump or relay as a potential solution.
Stangnet Members: Please make suggestions/corrections to above as you will probably see it again.
