RORERI: A JDM 1992 ST185H-BLMVZ

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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby Roreri » Sun Sep 11, 2022 10:16 pm

I'm shopping for a fuel pressure regulator that will work with a Gen 2 3S-GTE.

The OEM part (Toyota 23280-74070) is not available.

Does anyone have any advice to give on this topic? I'm looking to hook something into the stock fuel rail. I am not looking for a large pressure increase from the 42psi standard.
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby Tippo » Sun Sep 11, 2022 10:20 pm

Roreri wrote:Okay...long story short, the Lorelei's performance issue was not solved by installing a new fuel pump.

I got the hardline flare nut lashed down and it's solid. The flare nut is an embarrassment now and someday I ought to have it replaced, but it's secure.

I was hopeful, but...on the check ride I observed the same disturbing fuel pressure drop and lean conditions as before.

Further, I filled the tank to the click stop, and it leaked as before--the new gaskets did not solve that issue. Maybe it's the bent tube gasket--which I did not replace but only reconditioned with AT205 Reseal. I did figure out through putting in an initial 5 Gallons plus 13.4 Gallons at the local gas station that it's 18.4 Gallons to the click stop. My old procedure of adding 10 Gallons at 1/4 tank is probably the way to go.

When I got back, I did a voltage drop test and here's what I got:

Voltage Drop FP and B+ Jumped 10 Sep 2022.JPG

With FP and B+ jumped at the diagnostic box, I saw pretty severe voltage drop--2.375 volts on average across two different multimeters. I found this difficult to believe which is why I did it twice, but my observations bear it out: While driving, I never at any time see the rich conditions and power that was routine even a couple of months ago. Any time I attempt to go WOT and achieve boost, the mix goes lean and fuel pressure drops. I can, however, drive at vacuum or zero boost just fine. It's like I have my 1991 Celica ST all over again--only worse.

Voltage drop of 2.38 volts is verified or at least further evidenced by a check of the voltage at the terminals and the voltage in the pump circuit. 14.55 volts minus 12.17 volts equals 2.38 volts.

Voltage at Terminals and Voltage to Pump 10 Sep 2022.JPG

As bad as that is, the voltage drop with the fuel pump relay installed is horrific:

Voltage Drop Comparison Fuel Relay In 10 Sep 2022.JPG

Though the readings were not consistent between multimeters, they were taken at different times and under different conditions. Both are terrible and the observed driving performance is what you would expect: Awful. Like, turn around at the end of the block and come back home bad.

However, voltage drop is not the whole of the story, I believe. I rigged up a direct line with 14G stranded automotive wire from the battery terminals to the fuel pump harness in the rear compartment, and set up a switch on the line in the cabin. The pump draws 12.3 volts when switched on without the motor running, and 13.13 volts at idle. I didn't do a voltage drop test with this setup--tonight. It's basically like a kill switch. I turn the pump on, it pressurizes the system, I turn the motor over, and we're off. I can definitely hear the new pump whining away back there, what with the rear seats down. The original pump was much quieter or at a frequency my military grade hearing could not pick up.

I took the Lorelei on a check ride with this situation in place and performance was better. I still observed leaning out under boost, but I could achieve mild boost--2.8psi--at 14.5:1. Pushing more resulted in leaning out and fuel pressure dropping. I have been running the same test loop throughout all of this, and I live on a bitch of a hill--I was able to motor on up it, at least, when I've had difficulty finding the right throttle setting before.

So, my thoughts? The fuel pump is only part of the issue. I think one, I need to address the fuel pump wiring harness, and two, I need to investigate the fuel pressure regulator. Possibly, a new fuel relay might help. Hell, until I look into it, it might be the entirety of the issue!

Grounding was another possibility I was advised to check: I have checked grounding and while I have not visually inspected every ground wire strap, I've touched the multimeter to various points and combinations and every reading is within what I've read is correct.

The work continues...



What a PITA, but sounds like you're on the right track. Doesn't hurt to replace the fuel pump as it definitely looks like it had some nasty buildup in it. Aside from that, the relay ore regulator is my bet. Unless there was a short/grounding or some rodents, unlikely a wire harness is no good. That would be a last resort for me. Mirum has a similar fuel delivery issue on lean condition, but it's most likely the ECU on that.
1992 SW20 MR2 Turbo 4th Gen 3SGTE Swap. Aquamarine Pearl. "Priscilla"
1992 ST185 Celica All-Trac Turbo 4th Gen 3SGTE Swap. Teal Metallic. "Lazarus"
1990 ST185 Cellica All-Trac Turbo. Grey Metallic. "Mirum"
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby Roreri » Sun Sep 11, 2022 10:34 pm

I have a replacement fuel pump relay on order and will try that.

I took a drive today, and monitored the pump current. Started out at 13.64 volts, and this slackened throughout the trip to 12.9 volts by the end of an hour cruise.

I strongly suspect that the fuel pressure regulator innards have given out, and the FPR is allowing too much fuel back to the tank--it won't allow pressure buildup to the injectors. That's my hypothesis. I mean, on top of the fuel pump being voltage starved.

I just need some advice on what aftermarket FPR and hardware I ought to collect up to effect the correction.

I have done a shitload of work on this bad boy and corrections there have been none.
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby underscore » Mon Sep 12, 2022 4:33 am

I'm a bit tired at the moment but isn't the larger voltage drop with the relay installed normal operation? From my understanding at low load the relay feeds power through the resistor, resulting in less voltage across the pump and less flow. Then at higher load it bypasses the resistor so the pump sees full voltage.
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby Roreri » Mon Sep 12, 2022 11:25 am

I guess I’ve been tired too. That is eminently sensible. At idle I suppose something like that would be expected. It’s just that it doesn’t kick in the higher voltage when needed—at least from what I’m observing in driving.

I’ll have a new fuel pump relay on Tuesday evening, so I’ll see…
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby Roreri » Tue Sep 13, 2022 12:31 am

With some help from a fellow allTrac-er I found out about this solution: https://racerxfabrication.com/mr2-celic ... or-adapter

RacerX Bosch Fuel Pressure Regulator Adapter.JPG

It allows the use of readily available Bosch 3 and 4-Bar FPRs, but does require some work to mate the return line output to the return line.

RacerX offers the option of a 3Bar or 4Bar FPR with it. The sole review said that he used an adjustable Bosch FPR. This guy from ECS Tuning: https://www.ecstuning.com/b-ecs-parts/a ... 198501blk/

Adjustable Fuel Pressure Gauge ECS Tuning Part Number 5705.JPG

Now...this would be a $254 parts bill.

Given that a non-adjustable Bosch fpr adds $45, that means $130 extra for adjustable and an inline fuel pressure gauge.

Alternately, I could try an Aeromotive 13109 for $209--hell, $164 from Aeromotive's Amazon store or Summit: https://www.amazon.com/Aeromotive-13109 ... B000CFSL1I

Aeromotive 13109 Fuel Pressure Regulator.JPG

But I am told that I would need about $XX in hardware to make this one work with the stock fuel rail...

Thoughts?

Option One: RacerX Bosch FPR Adapter and Bosch 3 or 4 Bar FPR. $124

Option Two: RacerX Bosch FPR Adapter and Bosch Adjustable FPR. $254

Option Three: Aeromotive 13109 Adjustable Fuel Pressure Regulator. $164 (plus $XX in additional hardware)

EDIT: The problem was not corrected by a new fuel pump relay. I assume I have two functioning fuel pump relays now, for whatever good that does me.

After weighing all of the factors, I've decided on the RacerX Bosch Fuel Pressure Regulator Adapter and the 3 Bar Bosch FPR. First, it will be the easiest to install. Second, it is the least cool factor option. Third, the cost is right.
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby alltracman78 » Wed Sep 14, 2022 2:19 am

This is what I was getting at when I mentioned you didn't understand what you were doing with the voltage drop test. You understand how to do the test in general, but you don't understand what it's doing or how to use the answers you're getting.

The point is to
A - see if you have a problem in the circuit
B - if you do have a problem, narrow it down til you find the specific problem(s).

If you find a problem in the circuit you have to keep breaking the circuit down and testing parts of it until you find exactly where the problem is.
Basically, you check the whole circuit. Then you break it in half and check each half. Then break each half down into half again. ect ect.
You don't need to break it down exactly in half; use natural points at connectors and/or connections.

Underscore is right, you should have some voltage drop outside of the pump with the FPR in "normal" mode. That's the FPR sending power through the FP resistor.

Your best bet to check the circuit is get one of those jumpers I mentioned so the FPR circuit is always in "power" mode. This removes the resistor from the equation completely. Makes it easier.

Once you have the FPR bypassed you check the circuit and if the voltage drop is too high (say anything above .2v or so) then you need to start breaking the circuit into smaller sections and checking each smaller section individually. This will narrow down exactly where the voltage drop is so you know exactly what to replace or repair.



I'm going to try to break some of this down specifically for your car.
First off I wouldn't worry (yet) about the voltage drop with the FPR.
Let's start easy(er) and go with the voltage drop when you jump FP and B+.
You shouldn't have any voltage drop here. There are no relays. Just wires and connectors. It helps that the wire is all the same color.

It is possible there are several bad connections or problems that are combining here. So don't skip any section(s) if you find one that has a high voltage drop. Keep checking the rest. The only time you can skip is if you check a section and it has no voltage drop. If you find no voltage drop in a section there's no need to break the section down further.
Also, I'm going off the US wiring diagrams. JDM is similar, but there may be some differences.
I'm going to assume you know how to locate the wiring connectors as well as which pin is which in the connector. If not you need to learn. Only going to type so much. :P

As you are breaking this down into segments you're going to be checking connectors that join 2 different wiring harnesses together. These will be some of your "break" points. It doesn't matter which side of the connection you back probe, as long as you use the same side to for both checks. If you use one side of the connection to check one segment and the other side to check the other segment you won't be checking the center of the connection and the pins and crimps for the connection itself.
I know that's a clumsy explanation, I can't think of a better way to explain it.

Key on.

1 - First break point is going to be at the DIAG box. We're going to separate the B+ side and the FP side.
-One MM(multimeter) probe on the positive battery terminal, the other on B+ in the DIAG box. If it isn't basically zero you have a problem in the B+ wiring. Hopefully not because there's a bunch of wires and splices in this circuit. Goes all through the engine harness plus some chassis stuff in the front. Will be a PITA.
-One MM probe goes to the FP port in the DIAG box, the other goes to the blue/black wire at the FP(Fuel Pump) connector. Should be basically zero again, but I'm guessing it won't be.

2 - Now we're going to break the FP part into sections. Engine harness and (several) body harnesses.
-Leave one probe on FP in the DIAG box. Other one goes to the IG2 connector (It's one of the 2 large harness to harness connectors attached to the outside of the ECU. White? I know JDM has this.). Find the corresponding blue/black wire and check. This is one single wire in the engine harness.
-One probe on the FP connector, blue/black wire, other probe on the IG2 connector blue/black wire.

3 - Breaking the chassis harnesses up. This is where I don't know how close the US wiring is to the JDM. So you may have to get creative. Though I'm guessing it will be on the same side because the FP is on the L side of the tank, so the wiring probably runs down the L side of the car for both US and JDM.
-One probe in blue/black wire on the chassis side of IG2, other probe in blue/black wire of IF1. On US spec this is in the drivers kick panel (L side where the large relay/fuse blocks are). Don't know if it will stay on that side or be on your drivers side (RH). This is your dash harness. Could be problematic because this harness is where FP splices into the regular pump circuit. Possible the splice is corroded.
-One probe on blue/black IF1, other probe on blue/black FP.

4 - Breaking up the last 2 chassis harnesses.
-One probe on blue/black IF1, one probe on blue/black BP1, which should be at the rear quarter panel. Roughly the side of the rear seat. This should run from the kick panel along the rocker panel to the rear seat area. One single wire.
-One probe blue/blak BP1, one probe blue/black FP. One wire that should run along the L rear quarter panel area to the fuel tank.

Couple more notes.
We didn't check across FP and B+ with the jumper installed. It's possible that was a bad connection.
This also doesn't check the wiring inside the fuel tank, it only checks to the pump connector at the top.
If you go to check the actual FP circuit, with the relays and all, you only need to check from IF1 (connection at the kick panel) to the battery. The circuit separates at that splice in the dash harness I mentioned above.

Hopefully that helps some.
And wasn't too detailed.
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby alltracman78 » Wed Sep 14, 2022 2:20 am

underscore wrote:I'm a bit tired at the moment but isn't the larger voltage drop with the relay installed normal operation? From my understanding at low load the relay feeds power through the resistor, resulting in less voltage across the pump and less flow. Then at higher load it bypasses the resistor so the pump sees full voltage.


100% Correct
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby alltracman78 » Wed Sep 14, 2022 2:23 am

Roreri wrote:I guess I’ve been tired too. That is eminently sensible. At idle I suppose something like that would be expected. It’s just that it doesn’t kick in the higher voltage when needed—at least from what I’m observing in driving.

I’ll have a new fuel pump relay on Tuesday evening, so I’ll see…


The relay should bypass the resistor at WOT.
Which you can tell by the ECU going from closed loop to open loop.
Unless it's already in open loop because of cold start or a problem.

I know I keep saying this, but once again, another reason to slap that jumper in there. Gets rid of that question.
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby alltracman78 » Wed Sep 14, 2022 2:28 am

Roreri wrote:With some help from a fellow allTrac-er I found out about this solution: https://racerxfabrication.com/mr2-celic ... or-adapter

RacerX Bosch Fuel Pressure Regulator Adapter.JPG

It allows the use of readily available Bosch 3 and 4-Bar FPRs, but does require some work to mate the return line output to the return line.



EDIT: The problem was not corrected by a new fuel pump relay. I assume I have two functioning fuel pump relays now, for whatever good that does me.

After weighing all of the factors, I've decided on the RacerX Bosch Fuel Pressure Regulator Adapter and the 3 Bar Bosch FPR. First, it will be the easiest to install. Second, it is the least cool factor option. Third, the cost is right.



I have zero experience with that. But the specs mention standard thread. Everything on our cars is metric. Every now and then you can mix the 2 and it will work. Just be careful because this is fuel.

FWIW I would have selected the same as you.
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby Roreri » Wed Sep 14, 2022 2:42 am

Alltracman78: This is amazingly detailed. I thank you for the time and hope to return the favor or pay it forward. When it comes time I will undertake to do this as you have described and document it. To my knowledge, the harness wiring is in the same place in the JDM chassis—they seem to have kept it that way.

Right now, I am running the fuel pump with a 14 gauge stranded wire direct feed from the battery. If there is a voltage drop issue it resides within the tank. That is, regrettably, possible. I did not undertake to replace all of the wiring there as I now know I should have.

I am going to install a new Fuel Pressure Regulator and then give it a check ride. If that fails to solve the problem then I have to continue to check.

If I have to drop the tank then I will replace all the wiring and also install a foam isolator because damn the pump is loud. I may go so far as to put an uprated fuel pump in there. Just because.

If it’s not fuel pump voltage drop or fuel pressure regulator I wonder what the hell else it could be.

Gratifying to know the simplest fuel pressure regulator solution is what you would have gone with. Trying to keep it all within the bounds of sensible.
Last edited by Roreri on Thu Sep 15, 2022 2:41 am, edited 1 time in total.
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby underscore » Wed Sep 14, 2022 5:35 am

One thing to add is when you're checking the wiring don't forget to check the ground side as well.

I'm still running a stock fpr but if I ever need to replace it I'd lean towards the same setup you picked so I'm interested to hear how the install goes and what you think of it.
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby Gert » Wed Sep 14, 2022 8:44 am

If I read correct: the stock resistor is still in place and used? Why?

I ditched the resistor decades ago and bridget the relay. No problems at all.
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby Roreri » Wed Sep 14, 2022 5:41 pm

Thanks all for supporting my work. I feel like I’m just flailing about a little.

Gert good point and I agree. I’m just having trouble sourcing one is all. Lots of distractors/limited time/yada yada.

Underscore thanks for the heads up and reminder to check the ground side as well. It’s rather complicated to a duffer like me. I’ll try.

I’m hoping that the fuel pressure regulator is the actual cause of the problem. If replacing the fuel pressure regulator doesn’t fix it, I’ll have won the booby prize for least wise analysis of this problem. Because at that point I will have:

Replaced the fuel filter
Replaced the spark plugs
Replaced the ignition wires
Replaced the distributor cap and rotor
Recapped and even replaced the ECU
Had the injectors cleaned checked serviced and o-rings replaced
Replaced the fuel pump relay (irrelevant I know)
Replaced the fuel pressure regulator

The consolation of course is doing all that was a good idea anyway.

Anyway parts are on their way.

The very first thing I’ll need to do is try and figure out if there’s resistance in the in tank wiring. And if there is, well, then I’ll drop the tank and rewire it.

As far as voltage drop/electrical: I ran a direct 14g line from the battery to the wiring just outside the fuel tank in the rear compartment. Was that fat enough wire? This bypassed (almost) ALL of the harness as far as power is concerned.

Since I have that stainless braided hose hooked up to the banjo bolt atop the fuel filter, I guess I could do a timed flow test to see what the fuel pump is flowing.
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Re: RORERI: A JDM 1992 ST185H-BLMVZ

Postby autojumbled » Thu Sep 15, 2022 7:39 am

Gert wrote:If I read correct: the stock resistor is still in place and used? Why?

I ditched the resistor decades ago and bridget the relay. No problems at all.


How do you bypass the fuel pump resistor?

I'm following this thread with interest - I've spent a couple years on and off chasing down a backfire at 4K revs. The rest of the car runs great and just cannot get to the bottom of it.
Kinda comforting that I'm not the only one that has un-diagnosable issues! :lol:
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