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Vr4 hard start, no start when hot

jduke0308

Active member
Joined
Apr 20, 2011
Messages
32
Location
Aurora, CO
Just had the motor rebuilt but when i go to start it it takes awhile to start. Sometimes needing me to give to a little gas while cranking to get it to start. I replaced the coolant temp sensor with a oem mitsu one and still same issue. Car Does have a walboro with the the rewire as well. Tried swapping ecus and got the same results. When its all warmed up and hot if i turn it off she will not start until its cooled down a lot. Where should i turn my attention to next? Also coolant temp gauge doesn't want to get warm either, stays below the first tick on the oem gauge. Possibly related or totally unrelated?
 

transparentdsm

Well-known member
Joined
Jul 27, 2011
Messages
3,690
Location
Cherry Hill, NJ
in my experience this has been the most common issue:

CTS wiring harness. you'll have to trace the wires back and find where there corroded or broken.
 

FlyingEagle

Staff member
Joined
Mar 5, 2005
Messages
1,635
Location
THE Ottawa
Quoting jduke0308:
Just had the motor rebuilt but when i go to start it it takes awhile to start. Sometimes needing me to give to a little gas while cranking to get it to start. I replaced the coolant temp sensor with a oem mitsu one and still same issue. Car Does have a walboro with the the rewire as well. Tried swapping ecus and got the same results. When its all warmed up and hot if i turn it off she will not start until its cooled down a lot. Where should i turn my attention to next? Also coolant temp gauge doesn't want to get warm either, stays below the first tick on the oem gauge. Possibly related or totally unrelated?



Coolant temp gauge uses a separate sensor from the one the ECU uses to determine it's mapping.

Check the sensor at the thermostat housing (two wire for ECU) as mentioned by the last poster, and check for a sensor being plugged into a single spade connector (single wire for gauges/cluster).

Also, do you have a FPR solenoid still wired into place, up on your firewall?

Not sure if the VR4 has it there, but it will be close and will be Tee'd into the vacuum hose going down to the FPR on the side of the fuel rail.

If the CTS does turn out to be an issue, I am also wondering if you might have a two fold issue altogether.
 

GSTwithPSI

Well-known member
Joined
Jan 1, 2012
Messages
3,461
Location
SoCal
Quoting transparentdsm:
in my experience this has been the most common issue:

CTS wiring harness. you'll have to trace the wires back and find where there corroded or broken.



^Yep. Your ECU isn't seeing coolant temperature. You need to figure out why.

From another thread with someone having the same issue:
Quoting GSTwithPSI:
You need a DVOM with long leads. I put my meter on the windshield of the car, and clamp one lead on the wire at the sensor connector. Then, I take the other lead and probe the ECU pin while looking at the meter through the windshield.

Coolant temp sensor wiring:
T-pin front: Coolant temp sensor (connector B02): Green/black (crossbar of T) and yellow/green (stem of T position)

First, clamp a meter lead on the Green/black (crossbar of T, or top part of the T) wire at the sensor.

Then, you need to find pin 20 at the ECU: ECU Pinout. Put your meter lead there, and see if there is continuity between the ECU pin, and the sensor connector. If not, then your ECU is not getting a signal from you coolant temp sensor. And, I'd bet my life that it isn't getting one.

The other wire, yellow/green (stem of T position) goes to ground. It goes to the ECU sensors ground on pin 24. You can do the same thing for this circuit as you did for the other, or you could just ground it somewhere in the engine compartment. Eventually, you want to make sure it is properly grounded through the engine harness back to the ECU though.

If your car isn't seeing coolant temperature, it is screwing all kinds of sh*t up. You need to verify it is working. It would be best if you had a logger or something, that way you could hook it up and see exactly what the ECU is seeing...

Lastly, here is a link to the library where the coolant sensor wiring diagram is located. click Look on page 148 (actual document page number, not the Adobe page number)




Threads: click and click
 

AllanL

Well-known member
Joined
Aug 4, 2008
Messages
294
Location
NV
doesn't the CTS throw an error and lights up the CEL?

i'm just confirming because this might also be an issue of a friend's car.

thanks!
 

ktmrider

Well-known member
Joined
Sep 10, 2007
Messages
3,128
Location
Tempe, AZ
Quoting AllanL:
doesn't the CTS throw an error and lights up the CEL?

i'm just confirming because this might also be an issue of a friend's car.

thanks!

So long as the ECU "sees" a signal ( when bad it will register -40 degrees ) no CEL. A full open/short would pop a code.
 

AllanL

Well-known member
Joined
Aug 4, 2008
Messages
294
Location
NV
oh, so as long as it is getting some 'feedback' from the sensor, CEL will remain off.

cut signal wire, or ground, then CEL on.

great!

thanks!
 
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