Wont start after driving for a while..

maxaud

Active member
Took this to my local Auto Electric location who are pretty good with electrical items and they're telling me the ECM isn't always signaling the fuel pump to turn on and recommend putting a new ECM. Looks like the ECMs are different between USDM and JDM. I found the pinout diagram for the st185H CS, I assume it's the same as the st185H RC? Anyone have a JDM one laying around part number 89661-2B310?
 

underscore

Well-known member
Did they open is up and take a look at the capacitors? Given the age of these cars they're likely to start drying out.
 

FC Zach

Active member
underscore":7tinwc4l said:
Did they open is up and take a look at the capacitors? Given the age of these cars they're likely to start drying out.

Yep, I've had this happen too.
 

FC Zach

Active member
You may be able to repair yours. Not the case for me, unfortunately I had to replace this ECU since the tracers were burnt too.

26480851264_eb5d2be562_z.jpg
 

maxaud

Active member
Anyone known which ones can be interchanged with the one I have. 1992 ST185H with W2A Intercooler.
 

underscore

Well-known member
Which MAF do you have? If you're running an RC MAF and ECU then you'll need another RC ECU. The CS and GrpA ones *should* interchange as well. If you feel like taking a long drive to Kelowna you're welcome to try mine and see if it works any better.
 

maxaud

Active member
underscore":2gj3nxu1 said:
Which MAF do you have? If you're running an RC MAF and ECU then you'll need another RC ECU. The CS and GrpA ones *should* interchange as well. If you feel like taking a long drive to Kelowna you're welcome to try mine and see if it works any better.
Yeah, It's all the stock RC stuff currently.
 

3s_woob

Member
I'm dealing with the same issues. Here's the write ups on the failing capacitors. looks like even if the tracers are bad you can still by pass them with jumper wire.

issues...
http://www.gt4dc.co.uk/forum/viewtopic.php?f=13&t=7566

repair
http://www.gt4dc.co.uk/forum/viewtopic.php?f=2&t=5617

detailed write up...
http://www.clublexus.com/forums/ls-1st- ... citor.html

my co-worker is good at soldering and working with circuit boards so he's going to have a crack at it. let you know the outcome.
 

alltracman78

Active member
I don't know if it's your ECU man; the fuel pump doesn't use the ECU to start running, it uses the starter signal for that.
Once you cut the starter THEN the ECU takes over control. So if your ECU is the problem it should start then die.
I'm not going to tell you there's no way it could be the ECU, but it's pretty unlikely IMO. More likely is 1 of the 2 relays for the pump.

The pump control relay is easy to jump if you don't want to spend the money on it. If that doesn't fix it pick up a new COR [Circuit Opening Relay] and throw it in.

As far as your ECU, you "need" an RC ECU. A Grp A or CS one will probably work find also, judging by how the US vs JDM ECUs work.
Also FYI; Either a 92/93 JDM or an RC ECU will both work find plugged into a US 92/93 harness, no wiring needed [The RC will throw a CEL because it doesn't have the IC level sensor hooked up, but the engine will run fine].
With that said, I'm guessing a regular JDM or US 92/93 ECU will run the engine fine plugged into an RC harness. I can tell you with certainty it won't have any problems with the RC AFM because I've ran and RC ECU on a regular AFM and a regular ECU with an RC AFM [I wanted to see what would happen with both. Nothing at all, ECU didn't even notice].
I don't know if either would control the IC pump though. But just to check for starting, I'm guessing they would both work.

Something else you can try is jumping TE2 and E1, leaving the jumper in and seeing if you get any codes when it does that. Unlikely, but worth a shot IMO. And it's free.

I hope that all made sense. GL :)
 

maxaud

Active member
alltracman78":1ry9mrql said:
I don't know if it's your ECU man; the fuel pump doesn't use the ECU to start running, it uses the starter signal for that.
Once you cut the starter THEN the ECU takes over control. So if your ECU is the problem it should start then die.
I'm not going to tell you there's no way it could be the ECU, but it's pretty unlikely IMO. More likely is 1 of the 2 relays for the pump.

The pump control relay is easy to jump if you don't want to spend the money on it. If that doesn't fix it pick up a new COR [Circuit Opening Relay] and throw it in.

As far as your ECU, you "need" an RC ECU. A Grp A or CS one will probably work find also, judging by how the US vs JDM ECUs work.
Also FYI; Either a 92/93 JDM or an RC ECU will both work find plugged into a US 92/93 harness, no wiring needed [The RC will throw a CEL because it doesn't have the IC level sensor hooked up, but the engine will run fine].
With that said, I'm guessing a regular JDM or US 92/93 ECU will run the engine fine plugged into an RC harness. I can tell you with certainty it won't have any problems with the RC AFM because I've ran and RC ECU on a regular AFM and a regular ECU with an RC AFM [I wanted to see what would happen with both. Nothing at all, ECU didn't even notice].
I don't know if either would control the IC pump though. But just to check for starting, I'm guessing they would both work.

Something else you can try is jumping TE2 and E1, leaving the jumper in and seeing if you get any codes when it does that. Unlikely, but worth a shot IMO. And it's free.

I hope that all made sense. GL :)

Thanks for all the info. I've sent the ECU off to get rebuilt so we will see if that fixes it or if I'm just throwing more money at it and go from there.
 

FC Zach

Active member
maxaud":2bti6rn5 said:
Was having the issue of not starting this weekend so I bridged the Fp and B+ in the diagnostic port and it started right up. Maybe it's the fuel pump relay but if it's going bad, I'm curious if there is something somewhere else that is making it go bad.

When all signs point to a relay that has been mentioned already and you confirmed operation by bypassing it, why would you speculate an ECU issue? ?

maxaud":2bti6rn5 said:
. . . I've sent the ECU off to get rebuilt so we will see if that fixes it or if I'm just throwing more money at it and go from there.

Unless you have another underlying issue, I'm afraid you may be doing just that. . Fix the problem before adding more variables. :)
 

maxaud

Active member
Well, the ECU company "rebuilt" the ECU and sent it back and the car wasn't working so it was sent back in again and now the company says they cannot rebuild it.

I cannot remember what the shop told me but was pretty sure the ECU wasn't sending the proper signal that the fuel pump was working or it did it intermittent.

What are my options for replacing the ECU with a new one? Is there a standalone system that works well on the ST185H?
 

underscore

Well-known member
If the fuel pump signal is the only issue why not just change the wiring so the fuel pump is tied directly to the ignition on?
 

FC Zach

Active member
FC Zach":1ro1biwi said:
maxaud":1ro1biwi said:
Was having the issue of not starting this weekend so I bridged the Fp and B+ in the diagnostic port and it started right up. Maybe it's the fuel pump relay but if it's going bad, I'm curious if there is something somewhere else that is making it go bad.

When all signs point to a relay that has been mentioned already and you confirmed operation by bypassing it, why would you speculate an ECU issue? ?

maxaud":1ro1biwi said:
. . . I've sent the ECU off to get rebuilt so we will see if that fixes it or if I'm just throwing more money at it and go from there.

Unless you have another underlying issue, I'm afraid you may be doing just that. . Fix the problem before adding more variables. :)

I'm still curious about this? ?
 

Magroo

New member
FC Zach":12ewz47a said:
FC Zach":12ewz47a said:
maxaud":12ewz47a said:
Was having the issue of not starting this weekend so I bridged the Fp and B+ in the diagnostic port and it started right up. Maybe it's the fuel pump relay but if it's going bad, I'm curious if there is something somewhere else that is making it go bad.

When all signs point to a relay that has been mentioned already and you confirmed operation by bypassing it, why would you speculate an ECU issue? ?

maxaud":12ewz47a said:
. . . I've sent the ECU off to get rebuilt so we will see if that fixes it or if I'm just throwing more money at it and go from there.

Unless you have another underlying issue, I'm afraid you may be doing just that. . Fix the problem before adding more variables. :)

I'm still curious about this? ?


In my experience its most likely a failing fuel pump relay. The ecu may be going bad also, but if FP and B+ can be jumpered then start there.

The relay is a spdt (single pole double throw) that's kicked on by the circuit opening relay, that's triggered by the ignition switch. The ecu side only switches between high and low state. Its a green wire with a red stripe

If the wiring and related check out, it could be the ecu side of things. When the ecu first gets power it sends a priming pulse(ground side switching, green wire red stripe) in the high state to bring the fuel system up to pressure. You should hear the fuel pump relay click on and off and the whirring for the fuel pump for about 1 to 2 seconds.

Another culprit may be the cold start injector side of things.

This is a very similar issue that I had before I ditched the stock ecu and went megasquirt. I had relay, wiring, and a bad ecu.
 
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