RORERI: A JDM 1992 ST185H-BLMVZ

Roreri

Active member
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.
 

underscore

Well-known member
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.
 

Gert

Active member
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.
 

Roreri

Active member
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.
 

autojumbled

New member
Gert":3fdfult5 said:
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:
 

alltracman78

Active member
autojumbled":1jhub85k said:
How do you bypass the fuel pump resistor?

Seriously?! :lol:
Covered multiple times in this thread alone. Fuel pump relay either sends power to the fuel pump resistor or bypasses the fuel pump resistor.
To eliminate the fuel pump relay and bypass the resistor you install the jumper that's been mentioned.

Roreri":1jhub85k said:
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.
You're welcome. Pay it forward. I have a mountain of people behind me that have explained, shown, and helped me. The world's a better place if people are informed IMO.

Roreri":1jhub85k said:
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.
Just the power side? Interesting you haven't fried the wire. Usually if the power is a larger gauge than the ground the ground wire will melt because current is the same throughout the entire circuit and the larger power wire allows more current to flow than the thinner ground can handle.

Roreri":1jhub85k said:
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.
Factory pump, right? Weird it's so loud, Toyota pumps usually aren't.

Roreri":1jhub85k said:
If it’s not fuel pump voltage drop or fuel pressure regulator I wonder what the hell else it could be.
You're going off the actual fuel pressure dropping, right? Not off A:F or something?

Roreri":1jhub85k said:
Thanks all for supporting my work. I feel like I’m just flailing about a little.
Happens to the best of us.


Roreri":1jhub85k said:
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 thought you already did? And got .2 Something volts?

Roreri":1jhub85k said:
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.
No booby prize. Good stuff to do anyways. And you need to eliminate one problem and one possibility at a time. No matter how good you are you don't always get it right the first time. Process of elimination.
 

Gert

Active member
autojumbled":29e9jcrk said:
How do you bypass the fuel pump resistor?
Connect pin 1 (blue/orange) with 4 (blue/black).

Fuelpump%20relay%203SGTE
 

Roreri

Active member
alltracman78":2ewhma6b said:
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.

Well, you sir were correct. The threads did not mate. So, now I guess my next step would be to get a new fuel rail and oh why the hell not 550cc injectors...

Or try and find some kind of metric (size?) to 3/4-16 RH thread adapter.

Now I am in the rabbit hole.

EDIT: Okay. I gave it some thought--I have no need for a new fuel rail or moar injectors--and had some good advice (thanks grip-addict!). I was able to see that the 3/4-16 to -8AN ORB fitting at the bottom of the RacerX fuel pressure regulator adapter was removable...

RacerX Bosch Fuel Pressure Regulator Adapter Bottom Removed.JPG
So, I put these on order from Racetronix:

Racetronix Order 17 Sep 2022.JPG
The first one replaces the 3/4" male thread on the bottom with M12 and allows the RacerX adapter to be mounted directly to the stock fuel rail without adding height--crucial as it is a tight AF install. It may require a little, ah, adjustment of the surrounding environment even as is.

The third one hooks into the return line -8AN ORB output, and reduces to -6AN ORB Male.

The middle one threads onto that -6AN ORB Male and allows the stock fuel return line to be pushed onto the 5/16" barb and then clamped.

Thankfully, somewhere out there in the world there's an adapter or three to make whatever you need to do work. Onward and upward!

Additional answers to you alltracman78:

1. Regarding the direct power feed--I did both the power and ground with 14G stranded wire.

2. Denso pump. It does seem to have quieted down. I really effing hope so because I do not want to drop the tank again anytime soon because it was a mfer (for a wuss like me).

3. Yes, I'm going off of the actual fuel pressure (tapped off a banjo bolt adapter to a physical gauge mounted on the hood where I can see it).

4. I did get a little voltage drop on the ground side--.2 was what I got.

Thanks for the support--it certainly is a process of elimination. I have the parts on order to replace the fuel pressure regulator, which grip-addict told me cured his similar symptoms a while back. If not, then I'll go deep on the electrical harness. And if I cannot figure it out I will take it to a specialist and pay the money and have an FMIC installed as well.
 

alltracman78

Active member
^Awesome.

Changing adapters is all you need to do. I was going to say I thought the thread was either 10 or 12mm x 1.0.

Don't add extra stuff right now (injectors). Figure your problem out first. THEN start modding.

The heat soaked intercooler may cause driveability issues. It won't cause low fuel pressure. Don't worry about it until you figure this out. Keep it simple. :)

The voltage drop on the ground side is fine. It's a TINY bit high, but not worth digging out IMO.

Remember how dirty your fuel in the tank was? That new fuel filter may be gunked up, at least somewhat. I would replace it again. I don't think it's necessarily causing problems, just good business.
I still don't like your tank being rusty inside, but everything can't be perfect. Just keep that in the back of your head and your fuel as full as possible.

Your battery voltage isn't dropping when the fuel pressure does, is it? I assume no, but that would be an obvious issue.


autojumbled":277te7ap said:
How do you bypass the fuel pump resistor?

Sorry, wasn't trying to embarrass you. I figured it was self explanatory.

The jumper I've been discussing only installs one way. If you pick one of them up, go to the relay box right in front of the alternator, remove the yellow relay in the relay box and install that jumper.
You can make your own jumper out of spade terminals and wire, I just like that the factory one fits perfect and looks like it belongs.
Toyota didn't use the fuel pump relay in the 5SFE cars but they did keep the wiring similar. So they put this jumper (they call it a short pin) in the relay box instead of the relay.
Does that make sense?
 

Roreri

Active member
All of that makes sense alltracman78. I will get it right first then consider the FMIC.

I hear you on the possibility that the fuel filter is dirty. I am not looking forward to changing the fuel filter. Last time I tried I ended up giving up and taking it in to a shop and getting charged $300 for the work. I was grudgingly okay to pay it though because I sure wasn't making any headway on it!

I got the adapters from Racetronix. Everything worked as advertised, though the threads were tight! I had to clamp the adapter down on the workbench and wrench the M12 to -8AN ORB adapter onto the bottom of it. The threads mating to the fuel rail were similarly tight but went on very snugly.

Fuel Rail with RacerX Bosch FPR Adapter 20 Sep 2022.JPG
That wasn't the only thing that was tight. The 3S-GTE engine bay is notoriously crowded, and the OEM fuel pressure regulator was pretty small and the surrounding piping was arranged with that in mind. I got the adapter in, but as you can see these two coolant return lines were displeased with the arrangement and had to be adjusted.

Adapter in Place 20 Sep 2022.JPG
I had to cant the return line output so that I could put the -8AN ORB to -6AN ORB reducer and -6AN ORB to 5/16" barb on.

Racetronix -8AN ORB to -6AN ORB and -6AN ORB to barb.JPG
But tight though it was all went in. But I screwed the reassembly up. I missed the bottom washer on the cold start fuel line and so the system leaks. Dropped it actually on install and didn't notice. Luckily it fell all the way through the engine to the deck--found it lying there next to dripping fuel when I was doing the leak check. And the garage smells like gas. And the wife hates the smell. : (

I'll pull the intercooler and throttle body and get in there and put the washer on and check again.
 

Tippo

Well-known member
Roreri":28exvbf1 said:
Tippo":28exvbf1 said:
What do you mean by "talky" by the way? You check your rotor shields to make sure it wasn't rubbing? If they squeak that could be it, check your bolts too, make sure everything is tight.

They pop and grind. Exactly the way they shouldn’t with radial bearings.

I will do all of that which you recommend.


I understand what you mean now. The suspension is LOUD. Assuming it needs to break in but I know what you mean now lol. I have yet to take it anywhere, just adjusting and using the jack, the suspension definitely makes a bunch of noise. After 6km, you said this went away right? Hopefully it's just a break-in thing.
 

underscore

Well-known member
On the plus side since the fuel filter was done recently it shouldn't be all seized together like the old one would've been.
 

Roreri

Active member
Grip-addict I don’t know yet! I started it up, smelled fuel, cut it, looked below and saw the o-ring and knew I’d flubbed the cold start fuel line reassembly. Might know tonight. On my way home from work and once the Mrs. lets me know what’s required of me I’ll tackle it or not. But the bottom line is if it doesn’t fix the problem I have two possibles:

1. Fuel pump starved for voltage therefore reduced flow.
2. Clogged fuel filter reducing flow.

Tippo, you know what I mean now right!? LOL. Talky is the right word. So on the one hand I’m glad it wasn’t just me! On the other hand sorry it’s happening to you. On the plus side yes it went away. But it’s still coilovers so it will always be rougher than OEM.

Underscore yes, that would be the hope right? I probably ought to just count on it and get a new fuel filter on order.

I did install the short pin, which deleted the fuel pump relay.
 

underscore

Well-known member
I'm not sure if it would cause your exact problem, but another possibility I can think of is a partly clogged or damaged fuel line. I think that's about the only other part in the system anyways.
 

Roreri

Active member
That, too, has occurred to me but I have not wanted to admit it as a possibility.

The essential issue is lacking flow. Fuel pressure drops and air-fuel goes lean. That tells me less fuel than needed.

I’ll get it sorted eventually. After dinner I think I’ll go tackle the proper reassembly. If I can sort it out quickly enough then I’ll check ride it tonight.

EDIT: Everything I do makes it worse. Now I have a fuel leak from the base of the fuel pressure regulator adapter. Something about the threads, probably. Maybe was unable to snug it tight enough.

Impossible to tell if the installation of the fuel pressure regulator corrected the issue as the fuel system cannot hold pressure. However, for one brief shining moment right after turning over the motor I did have the pleasure of seeing the fuel pressure reach 43psi—the rated psi of the newly installed 3 Bar Bosch fuel pressure regulator. It was only reaching 39psi before, then dropping to 30 psi at idle.

So I know something changed.

EDIT EDIT: There are gasoline resistant thread sealants, like these:

Permatex Aviation Form-a-Gasket No. 3 Sealant: https://www.jamestowndistributors.com/p ... etail/9403

Gasoila E Seal Gas Pipe Thread Sealant: https://www.mfcp.com/product/gasoila/ga ... nt-ethanol

I like the specific formulation of the Gasoila E Seal for E10, and the temperature range up to 600 degrees F--not that the fuel rail reaches that, but more margin for safety is more margin for safety.

I could disassemble the whole thing again (it's becoming less and less intimidating with every iteration!), apply that to all the connection threads including the fuel return, put it all back together, and try again.

EDIT EDIT EDIT: Gasoila E Seal on the way. Once again I will take it apart and put it back together.
 

Roreri

Active member
I got everything apart and applied the Gasoila E Seal to the fuel pressure regulator adapter threads. I put it back on the fuel rail and am letting it cure.
 

alltracman78

Active member
My 2 cents on this is if sealant needs to be used on threads it wasn't assembled properly. Unless it calls for sealant obviously.
All that stuff should have O rings, metal crush washers or a flare to seal the system. If something is leaking it's not put together right or the part is faulty.
Especially important with fuel IMO.

Most times you will be fine, I'm just picky with this.

I hope that stuff isn't too much of a seal and you can get it apart again if you need to.

I also hate to be picking on what you're doing again. It's not meant in a bad way. I hope this solves it for you. :)
 

Roreri

Active member
I know. : (

No effing OEM fuel pressure regulator available made this whole process ridiculous.

There is an o ring and a washer. The issue is that full seat means the fuel return line adaptors point right into an immovable obstruction in the engine compartment which as we all know is not roomy or commodious. I could add a thicker washer. I am going to test it when i get home prior to reassembly.

If I have to go with a top feed fuel rail and new injectors I will.

I will do what is necessary.
 
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