Electrical signal not reaching fuel pump

[A.BuckShort]

RE: My 1993 Supra GTE (nonturbo) with approx. 160,000 miles. Owned since 1996.

Something is preventing the electrical signal from reaching my gas tank fuel pump, causing car to stall, every time, almost immediately after ignition. Test light at fuel pump starts to dim and goes out as pump slows and stops within about 2 minutes. Any thoughts?

Have already drained and cleaned out old gas residue, added gas treatment, manually cleaned throttle, installed new fuel pump and ECU relay. This seemed to solve original problem of not taking the gas and generally requiring starter fluid through the air filter to start after sitting overnight. Now starts without the starter fluid, but then began similar stalling when stopped at a traffic light or slowing for turns. Now above problem with losing electrical to fuel pump and test light, which may have been the real problem to begin with? Now starts without the fluid, but stalls quickly thereafter. Could it relate to however much the engine heats up after ignition?

I had seen some evidence of some kind of likely rodent infestation when initially opening the air filter to spray the starter fluid. Only thing we can think of right now is some animal might have chewed through wire going to the fuel pump somewhere– but uncertain how to look for that or if should be looking for something else?

[pwpanas]

Originally Posted by A.BuckShort

RE: My 1993 Supra GTE (nonturbo) with approx. 160,000 miles. Owned since 1996.

Something is preventing the electrical signal from reaching my gas tank fuel pump, causing car to stall, every time, almost immediately after ignition. Test light at fuel pump starts to dim and goes out as pump slows and stops within about 2 minutes. Any thoughts?

Have already drained and cleaned out old gas residue, added gas treatment, manually cleaned throttle, installed new fuel pump and ECU relay. This seemed to solve original problem of not taking the gas and generally requiring starter fluid through the air filter to start after sitting overnight. Now starts without the starter fluid, but then began similar stalling when stopped at a traffic light or slowing for turns. Now above problem with losing electrical to fuel pump and test light, which may have been the real problem to begin with? Now starts without the fluid, but stalls quickly thereafter. Could it relate to however much the engine heats up after ignition?

I had seen some evidence of some kind of likely rodent infestation when initially opening the air filter to spray the starter fluid. Only thing we can think of right now is some animal might have chewed through wire going to the fuel pump somewhere– but uncertain how to look for that or if should be looking for something else?

Minor point but GTE means turbo. GE is non-turbo.

I don't know the GE that well, but hopefully it's got enough in common with the GTE for me to help. On the GTE, there's an ecu that controls the fuel pump. It's function is to run the fuel pump at 9v off boost, and then switch to 12v when boosting. It's located on the inside of the left rear fender, behind the tire, and below (not behind) the plastic trim panel that covers up to the hatch. The GE might have something similar, just to help with fuel economy...so that'd be my first guess - that your fuel pump ECU has gone bad. If you know someone else with a GE, you could try to swap it?

If that's not it, or you want to try something else, just add a new fused circuit from your fuse box, and run a new wire back directly to your fuel pump. Ideally, you'd trigger this with a relay from an existing ignition-switched circuit. This would run your fuel pump at 12v continuously whenever your key is on, bypassing the fuel pump ecu. If this fixes the problem, it'd definitely isolate the issue to your fuel pump ecu or the fuel pump wiring.

Another thing to do would be to put your test light onto the 12v input line into your fuel pump ecu (again, assuming the GE has such a thing). If that line doesn't flicker, you eliminate a possible any wiring issue before that point. If you also test right at the fuel pump ecu's output next, and it does flicker, you've nailed the problem down to the fuel pump ecu for sure.

Hopefully some of that helps. If not, please ask more questions!

[A.BuckShort]

Phil '94 Thanks for reply. Sorry for taking so long to respond; this thing has been in the shop undergoing diagnostics for so long, I’m just glad they don’t charge storage like an impound lot. Quite possibly now as much "vertical" mileage on the lift as horizontal.

Actually just replaced the fuel pump relay ecu, and tried a few other things to see if/or why wire to fuel pump getting hot, etc. Latest consensus is probably likely the MAIN ecu (under passenger’s side dashboard) which allegedly had been repaired about two-three years ago (through Toyota dealership by a place that rebuilds things like that), and seemed to be working fine since. Does this sound like a possibility? If yes, does anyone on the forum know where I could find/get a replacement ecu for this 1993 Supra GE (assuming it’s an MKIV?). My wife wants her own Toyota SUV back. Is the "where to find" inquiry something I should post separately as a new post on this forum? As you may guess, I feel more than just automotively challenged.

[pwpanas]

Originally Posted by A.BuckShort

Phil '94 Thanks for reply. Sorry for taking so long to respond; this thing has been in the shop undergoing diagnostics for so long, I’m just glad they don’t charge storage like an impound lot. Quite possibly now as much "vertical" mileage on the lift as horizontal.

Actually just replaced the fuel pump relay ecu, and tried a few other things to see if/or why wire to fuel pump getting hot, etc. Latest consensus is probably likely the MAIN ecu (under passenger’s side dashboard) which allegedly had been repaired about two-three years ago (through Toyota dealership by a place that rebuilds things like that), and seemed to be working fine since. Does this sound like a possibility? If yes, does anyone on the forum know where I could find/get a replacement ecu for this 1993 Supra GE (assuming it’s an MKIV?). My wife wants her own Toyota SUV back. Is the "where to find" inquiry something I should post separately as a new post on this forum? As you may guess, I feel more than just automotively challenged.

I've heard of the pins in the main harness going bad, as well as the capacitors on the main ecu motherboard. The most common problem with the main ecu however, is the harness getting 'jacked with' when amateurs try to install piggyback items like fuel controllers or fuel cut eliminators.

This forum isn't that active for MKIV used parts, but I can give you a couple places to try if you'd like please PM me for that info.

[A.BuckShort]

OM PART # 89661-14580
Understand interchangeable with same configured 1992-95 Supras, 1992-05 Lexus 300s (and possibly Lexus 400s)? Is that correct? If so would the Lexus units have same OM part # 89661-14580?

Yes, he’s baaaaaaaack..........!

Greetings. You may remember me, the hapless bozo who first checked in here 2 whole months ago, inquiring if anybody knew why aforementioned vehicle kept stalling and not starting because of no electric signal getting to fuel pump.

Got some good advice here, including that problem may be in fuel pump ECU (the smaller, dedicated one), how to test for that, and also a feasible workaround with a fused direct wire ignition-to-fuel pump. (Had already replaced the fuel pump, fuel pump ECU, cleaned throttle, etc. – nada!) Further testing suggests it’s the MAIN (larger) ECU—which I understand may be common in Supras.

Seeming confirmation: shipped ECU core to Cardone Industries in Philly for rebuild and return. Came back as “ECU cannot be repaired.” No reason given, but my understanding is it’s the ones with fuel pump signal, circuitry, or fuel injection issues that are irreparable.

No great success finding a replacement unit, so far. Now understand can also take rebuilt or salvaged ECU from the years 1992-95 for above, as well as Lexus SC-300 and possibly SC-400; so still looking. Leads on unit or where to look are appreciated.

Since I don’t recall losing any other ECU-controlled functions at the time fuel pump quit, it looks like we may be able to get by with the existing crippled unit combined with the workaround suggested by Phil, for fuel pump portion. However, if possible, first would like to take another shot at maintaining the integrity of the structure with a replacement ECU unit from Supras or Lexi. Leads appreciated on available unit or even good places to look, and also would the applicable Lexus ECU have the same OM part #? Or would I at least have to determine if also automatic, nonturbo, non-Cal. emissions?

(FYI, have Googled/eBayed some possibilities. Tanin Auto Electronix (rebuild/return service in Racine, WI) says they will try to help look for a working replacement, but understand that may be kind of pricey if found.

Also tomorrow planning to contact ZK boys (aka SIA in Illinois) who have listed 1993 Lexus, naturally aspirated, SC300 ECU – but unsure yet if that’s for an auto trans, without Cal. federal emissions, or even it’s not actual unit available, but another inapplicable rebuild-return situation, as most of these turned out to be. Emailed inquiry Monday to OEM Auto Computer Parts in Miami, but have not heard back.)

I really appreciate this forum.
I can also be emailed directly at reb1000@sbcglobal.net.
Thanks.
Roger Burke

[Those gangsters in the supermarket parking lot who kept asking if I wanted to sell this sucker are now starting to look like a real missed opportunity ]

[pwpanas]

Originally Posted by A.BuckShort

OM PART # 89661-14580
Understand interchangeable with same configured 1992-95 Supras, 1992-05 Lexus 300s (and possibly Lexus 400s)? Is that correct? If so would the Lexus units have same OM part # 89661-14580?

Yes, he’s baaaaaaaack..........!

Greetings. You may remember me, the hapless bozo who first checked in here 2 whole months ago, inquiring if anybody knew why aforementioned vehicle kept stalling and not starting because of no electric signal getting to fuel pump.

Got some good advice here, including that problem may be in fuel pump ECU (the smaller, dedicated one), how to test for that, and also a feasible workaround with a fused direct wire ignition-to-fuel pump. (Had already replaced the fuel pump, fuel pump ECU, cleaned throttle, etc. – nada!) Further testing suggests it’s the MAIN (larger) ECU—which I understand may be common in Supras.

Seeming confirmation: shipped ECU core to Cardone Industries in Philly for rebuild and return. Came back as “ECU cannot be repaired.” No reason given, but my understanding is it’s the ones with fuel pump signal, circuitry, or fuel injection issues that are irreparable.

No great success finding a replacement unit, so far. Now understand can also take rebuilt or salvaged ECU from the years 1992-95 for above, as well as Lexus SC-300 and possibly SC-400; so still looking. Leads on unit or where to look are appreciated.

Since I don’t recall losing any other ECU-controlled functions at the time fuel pump quit, it looks like we may be able to get by with the existing crippled unit combined with the workaround suggested by Phil, for fuel pump portion. However, if possible, first would like to take another shot at maintaining the integrity of the structure with a replacement ECU unit from Supras or Lexi. Leads appreciated on available unit or even good places to look, and also would the applicable Lexus ECU have the same OM part #? Or would I at least have to determine if also automatic, nonturbo, non-Cal. emissions?

(FYI, have Googled/eBayed some possibilities. Tanin Auto Electronix (rebuild/return service in Racine, WI) says they will try to help look for a working replacement, but understand that may be kind of pricey if found.

Also tomorrow planning to contact ZK boys (aka SIA in Illinois) who have listed 1993 Lexus, naturally aspirated, SC300 ECU – but unsure yet if that’s for an auto trans, without Cal. federal emissions, or even it’s not actual unit available, but another inapplicable rebuild-return situation, as most of these turned out to be. Emailed inquiry Monday to OEM Auto Computer Parts in Miami, but have not heard back.)

I really appreciate this forum.
I can also be emailed directly at reb1000@sbcglobal.net.
Thanks.
Roger Burke

[Those gangsters in the supermarket parking lot who kept asking if I wanted to sell this sucker are now starting to look like a real missed opportunity ]

The workaround should be fine. Here's why. That fuel pump ecu's only job is to switch the fuel pump to 9v (vs 12v) under vaccum (i.e. no boost). This has two extremely subtle and nearly useless benefits:
1) on really long trips (200mi+), the fuel can warm up a bit ... which can affect the accuracy of the fuel pressure regulator to a very small degree. At 12v, the fuel pumps more volume, which means fuel takes more trips through the return line...eventually warming the whole tank of fuel up a bit. If I recall correctly, you'll run slightly leaner with a warmer fuel pressure regulator...which will actually improve your gas mileage. Conservatively, just don't push the boost to the max during a very long road trip if you're using the workaround.
2) running at 12v full-time consumes a bit more electricity on average, which is very slightly harder on the battery & alternator...and of course consumes a very slight amount more fuel.

Contrast that with many single turbo supras that run 2 or even 3 fuel pumps full time at 12v. I'm almost 100% sure there are no upgraded fuel system kits available for the Mkiv that provide for 9v ... especially on pump#2.

Oh, and for what it's worth, some aftermarket fuel pumps provided with aftermarket upgraded fuel kits actually can't even reliably run at 9v (eg. Walbro).

As most know, I bought my '94 Mkiv TT new in December '93. I'm as much of a 'purist' about keeping factory features/functionality (as much as practical) as almost anyone -but- I sincerely think the 9v fuel pump ecu/feature is superfluous. My advice: trigger a relay to run a new (fused) fuel pump circuit off any other circuit tied to the ignition and don't give it another thought.

[A.BuckShort]

Phil,

You may remember me. I’m the guy with the ’93 Supra (automatic/nonturbo) who corresponded back and forth with you last July about the problem I had with my ECU not relaying the signal to the fuel pump. Your excellent advice on this forum was:

“If that's not it, or you want to try something else, just add a new fused circuit from your fuse box, and run a new wire back directly to your fuel pump. Ideally, you'd trigger this with a relay from an existing ignition-switched circuit. This would run your fuel pump at 12v continuously whenever your key is on, bypassing the fuel pump ecu. If this fixes the problem, it'd definitely isolate the issue to your fuel pump ecu or the fuel pump wiring.”

Well, I’m still that guy and still have that problem. Because, instead, Amir, my mechanic and I just spent 9 month, buying and shipping Supra ECUs and would be replacement ECUs back and forth between their vendor and repair services – to ultimately conclude the first ECU repair service last summer was correct , the ecu I shipped them was irreparable. Since also learning NO Supra of Lexus ECUs we were able to find worked, and to boot, those were also not reparable for this fuel pump problem either.

[Another diversion has been that, although our search did not exactly proceed at “breakneck speed,” I did, in fact, literally break my neck -- same vertabra that eventually did in Christopher Reeve (known in medicine as the “hangman’s fracture , because that’s also what splits apart when they hang you). Fortunately, in my case, it did not damage the spinal cord, no paralysis, and full recovery predicted after about 2 more months sporting this traditional “halo” metal head stabilization collar screwed up against my skull. Although, on the bright side, on a good day I think it can pick up Radio Dubrovnik  I swear, not making this up, except for the last part.]

So the mechanic has finally agreed with me that 9 months is also the traditional gestation period for the ignition direct to fuel pump suggestion you made in the first place. I think what you described is pretty straightforward, and Monday I will get him a copy of your posted suggestion above. I’m not sure he was certain I could find that, but, in either case, he asked if I could get him your phone number in GA, in case he had any further questions?

If you would, you can email it to me at reb1000@sbcglobal.net. In return, I may just send you the most entertaining part of my injury which has almost made the whole adventure worthwhile. Again, I appreciate the interest you have taken I my Supra problem. Thanks.

Roger Burke (Supra Forum handle: A. Buck Short)
Dallas, TX
reb1000@sbcglobal.net

[pwpanas]

Originally Posted by A.BuckShort

Phil,

You may remember me. I’m the guy with the ’93 Supra (automatic/nonturbo) who corresponded back and forth with you last July about the problem I had with my ECU not relaying the signal to the fuel pump. Your excellent advice on this forum was:

“If that's not it, or you want to try something else, just add a new fused circuit from your fuse box, and run a new wire back directly to your fuel pump. Ideally, you'd trigger this with a relay from an existing ignition-switched circuit. This would run your fuel pump at 12v continuously whenever your key is on, bypassing the fuel pump ecu. If this fixes the problem, it'd definitely isolate the issue to your fuel pump ecu or the fuel pump wiring.”

Well, I’m still that guy and still have that problem. Because, instead, Amir, my mechanic and I just spent 9 month, buying and shipping Supra ECUs and would be replacement ECUs back and forth between their vendor and repair services – to ultimately conclude the first ECU repair service last summer was correct , the ecu I shipped them was irreparable. Since also learning NO Supra of Lexus ECUs we were able to find worked, and to boot, those were also not reparable for this fuel pump problem either.

[Another diversion has been that, although our search did not exactly proceed at “breakneck speed,” I did, in fact, literally break my neck -- same vertabra that eventually did in Christopher Reeve (known in medicine as the “hangman’s fracture , because that’s also what splits apart when they hang you). Fortunately, in my case, it did not damage the spinal cord, no paralysis, and full recovery predicted after about 2 more months sporting this traditional “halo” metal head stabilization collar screwed up against my skull. Although, on the bright side, on a good day I think it can pick up Radio Dubrovnik  I swear, not making this up, except for the last part.]

So the mechanic has finally agreed with me that 9 months is also the traditional gestation period for the ignition direct to fuel pump suggestion you made in the first place. I think what you described is pretty straightforward, and Monday I will get him a copy of your posted suggestion above. I’m not sure he was certain I could find that, but, in either case, he asked if I could get him your phone number in GA, in case he had any further questions?

If you would, you can email it to me at reb1000@sbcglobal.net. In return, I may just send you the most entertaining part of my injury which has almost made the whole adventure worthwhile. Again, I appreciate the interest you have taken I my Supra problem. Thanks.

Roger Burke (Supra Forum handle: A. Buck Short)
Dallas, TX
(972) 980-2522
reb1000@sbcglobal.net

Hi Roger,

I'm sorry to hear about your injury. However, it seems that you're in good spirits, and on the road to recovery. I hope that continues, and that you beat the expectation of fully healed in only two more months.

I'll definitely try to get in touch with you via email, as you suggested.

Kind regards,
Phil