Subaru XT 1986 ea82T starts and goes too 3k rpm the drops to 0

[86 xt]

Hi i Have a XT 1986 that starts but goes too 3k rmp then drops to 0, ran fine a week erlier, been started and moved a couple of times between that time with no start issue or idle issue, was on a drive a few days ago and the coolant temp got high then it started to jurk on the way  and now it starts but goes too 3k then down to 0

things i have checked is

spark is ok

fuel is ok

groundwires is ok

maf seems ok have tryed another one same problem

tryed disconnected the 02 sensor same problem

tryed switching the cts sensor other, might be bad aswell

the ECU gives 1 longer blink then 2 short trublecode 12.

any ides what could be wrong or what else to try?

kind regards from sweden

[czny]

Could be the 6 pin ignition relay which is above the ECM next to the steering column. There are 2 relays there held to a small bracket with a single screw.

The black Chinese replacements are junk & fail too quickly. Look for a brown Legacy ignition relay for 1990 to 1994 models.

I've had this happen to my 87 GL twice now, when I used the black Chinese relays they failed prematurely.  

You'll have to pull down the kick panel above the pedal cluster & remove the ecm to get at it.

https://www.rockauto.com/en/moreinfo.php?pk=3786111&cc=1269446&pt=3480&jsn=388

 

 

 

Edited January 22, 2023 by czny

[86 xt]

Thanks for the replay, will test this have a junk car that i can take parts from and will see if this solves it. 

[idosubaru]

17 hours ago, 86 xt said:

Hi i Have a XT 1986 that starts but goes too 3k rmp then drops to 0

Does it go to 3k immediately and die without running more than 2 seconds, or does it do it once you hit the gas pedal?  Or randomly?

Will it stay running if you keep your foot on the gas before it "drops to 0"?

Have you tried "read memory" mode to see if there's more codes than just that one?

Any modifications or recent work to the engine or wiring?

1. check/test/clean out the idle control valve - they get carbon build up and stick internally

2. Check fuel pressure.

3. Check the contacts/connector wiring of the CTS.  The contacts inside the connector get badly corroded so installing another sensor doesn't help.  It's also very common to need to replace the entire pigtail and some wiring if the corrosion has crept back up under the wiring insulation.  This is very common on these.  I've even cut a notch in the CTS sensor, cut the plastic connector off and soldered new wire directly to the CTS terminals to bypass bad old gen connectors and wiring.  There's a common fuel injector plug that's a direct fit but I'm not sure if 86 differ in anyway from 88-91 I'm more familiar with.

4. The wiring on these old engines tends to "break" and have poor contact inside the insulation very close to the connectors on the engines themselves.  And I've seen this happen with no trouble code/check engine light.  Massage the wiring from each connector where it plugs into the engine and your way back about 4-6".  Do this while the engine is running or trying to start multiple times. That's how I've found a few.  If it changes while you're doing it or throws a code - you found the issue.  CTS, idle control, throttle position.  Oddly even though there are far more of them I've not seen/heard of it happening to injector connectors. 

 

 

[86 xt]

18 minutes ago, idosubaru said:

Does it go to 3k immediately and die without running more than 2 seconds, or does it do it once you hit the gas pedal?  Or randomly?

Will it stay running if you keep your foot on the gas before it "drops to 0"?

 

 

 

It goes immediatly to 3k stays om 3k for 2 sec then goes to 0 and dies, can't keep it alive long with the gas pedal 

Will go though your list and see if anything can do the trick 

[86 xt]

19 hours ago, czny said:

Could be the 6 pin ignition relay which is above the ECM next to the steering column. There are 2 relays there held to a small bracket with a single screw.

The black Chinese replacements are junk & fail too quickly. Look for a brown Legacy ignition relay for 1990 to 1994 models.

I've had this happen to my 87 GL twice now, when I used the black Chinese relays they failed prematurely.  

You'll have to pull down the kick panel above the pedal cluster & remove the ecm to get at it.

https://www.rockauto.com/en/moreinfo.php?pk=3786111&cc=1269446&pt=3480&jsn=388

can't seem to find any relays next to the steering column maybe im blind or they are not there

 

 

 

 

[86 xt]

20 hours ago, czny said:

You'll have to pull down the kick panel above the pedal cluster & remove the ecm to get at it.

 

 

 

 

The ECM sits in the trunk on my 86

can the relays be behind the radio?

[czny]

22 minutes ago, 86 xt said:

The ECM sits in the trunk on my 86

can the relays be behind the radio?

Snake your hand over that antenna cable at top Left of pic & feel around on top of steering column for 2 relays - one round can & one squarish.

The round one is fuel pump relay & squarish one ignition relay.

If there, remove the black harness screws to get at little Phillips screw holding the relay bracket. If the relay rattles when you shake it one contact pair is broken.

If not there, someone with an XT shop manual needs to chime in. Only ones I have here are for GL/DL.

 

[86 xt]

22 minutes ago, czny said:

Snake your hand over that antenna cable at top Left of pic & feel around on top of steering column for 2 relays - one round can & one squarish.

The round one is fuel pump relay & squarish one ignition relay.

If there, remove the black harness screws to get at little Phillips screw holding the relay bracket. If the relay rattles when you shake it one contact pair is broken.

If not there, someone with an XT shop manual needs to chime in. Only ones I have here are for GL/DL.

 

Thanks, will look at this tomorrow and post an update waht i found.

thanks again for the replys

[idosubaru]

1 hour ago, 86 xt said:

The ECM sits in the trunk on my 86

can the relays be behind the radio?

88-91 XT relays are on the upper left of the photo you posted, above that brownish connector tucked agaisnt the side wall behind the fuse panel.

But how can a relay fail and still allow the car to start and run for a moment?  Sounds like a waste of time to me but maybe someone can chime in which relay (fuel pump?) and how they fail that allows them to prime and start but not run?

I'd pull the fuel line first and see if fuel flows out like normal.  Remove fuel clamp, point hose in bucket while priming and trying to start the vehicle. If you're not sure what the flow is supposed to look like video it and post a link.  It should roughly look like a garden hosing flow water. 

Or of course even better - the proper test is to put a Tee in with a fuel pressure gauge.

Edited January 23, 2023 by idosubaru

[1 Lucky Texan]

he did say fuel was OK, but I was gonna suggest trying some starting fluid in the intake to see if it will run longer.

[idosubaru]

3 hours ago, 1 Lucky Texan said:

he did say fuel was OK, but I was gonna suggest trying some starting fluid in the intake to see if it will run longer.

Ah I see that. Thanks. 
OP how do you know the fuel is good?  
that’s MPFI and requires more psi than carbed engines. 
 

starting fluid excellent suggestion.  

[czny]

On 1/23/2023 at 1:57 PM, idosubaru said:

88-91 XT relays are on the upper left of the photo you posted, above that brownish connector tucked agaisnt the side wall behind the fuse panel.

But how can a relay fail and still allow the car to start and run for a moment?  Sounds like a waste of time to me but maybe someone can chime in which relay (fuel pump?) and how they fail that allows them to prime and start but not run?

I'd pull the fuel line first and see if fuel flows out like normal.  Remove fuel clamp, point hose in bucket while priming and trying to start the vehicle. If you're not sure what the flow is supposed to look like video it and post a link.  It should roughly look like a garden hosing flow water. 

Or of course even better - the proper test is to put a Tee in with a fuel pressure gauge.

My apologies, I was thinking of GL/DL which uses 2 sets of contacts to supply power to the TBI ECM.

My GL behaved the same way as his XT - start, rise to 2000 + rpm, then die. Would not idle. 

Looked over the Haynes manual electrical schematic for 86 MPFI:

The green fusible link powers a single contact ignition relay to ECM on MPFI(wht/red wire).

Fuse 11 powers the fuel pump relay(blk/wht wire). Green fusible link powers fuel pump and Aux air valve(blu wire).

Edited January 25, 2023 by czny
schematic added

[Steptoe's photos]

It sounds like same as my 85 turbo when fuel pump failed to keep it up, so to speak. I t'd in a fuel pressure test gauge after the fuel filter. Done as a T in, not end of line or it won't reveal issues, I found.

I got the required 36 psi, while revving stationary on the spot, but when taped gauge to windscreen and drove off, pressure dived to 10 psi, spluttered and not died, but return to idle, pressure returned to 36. Repeated all procedures to check again, replaced pump with new after market pump. Sorted !

 

[86 xt]

On 1/24/2023 at 4:06 AM, Steptoe's photos said:

It sounds like same as my 85 turbo when fuel pump failed to keep it up, so to speak. I t'd in a fuel pressure test gauge after the fuel filter. Done as a T in, not end of line or it won't reveal issues, I found.

I got the required 36 psi, while revving stationary on the spot, but when taped gauge to windscreen and drove off, pressure dived to 10 psi, spluttered and not died, but return to idle, pressure returned to 36. Repeated all procedures to check again, replaced pump with new after 

I have bought a fuel pressure test gage and hope it arives soon, will post an update after the test. 

[86 xt]

the car start and goes to 3k rpm at 30psi of fuel pressure when the rpm is getting lower it goes up abit then down to 30psi and stalls

[1 Lucky Texan]

in 'the old days' cars had a start resistor and a run resistor that sorta had this symptom.

[86 xt]

but can't hear the fuel pump when the ignition is on, think i used to hear it, was kinda loud before when driven

Edited January 26, 2023 by 86 xt

[Steptoe's photos]

On 1/27/2023 at 7:44 AM, 86 xt said:

but can't hear the fuel pump when the ignition is on, think i used to hear it, was kinda loud before when driven

loud pump is not normal for these once engine is running. The ECU gives pump a priming power then safely shuts off power until started. Some issues can be sorted by check inspect all electrical connections especially for sensors and main ecu. A spray of electrical contact cleaner to help ...

[86 xt]

if I would buy a new fuel pump any suggestions on where to buy? 

[86 xt]

tested with another fuel pump but gave the same result.

[idosubaru]

On 1/29/2023 at 9:04 AM, 86 xt said:

tested with another fuel pump but gave the same result.

Did you test output in anyway - if installing another pump- run it before connecting the output hose so you can see it coming out and tell if it's muddy from internal tank rust. 

Was the sock on the old pump clogged at all?

If a used fuel pump was installed then there's no telling it's any good. I swapped 3 used fuel pumps in a 1987 XT years ago and all three pumps weren't usable. 

[Steptoe's photos]

On 1/30/2023 at 1:04 AM, 86 xt said:

tested with another fuel pump but gave the same result.

this was going to happen, but you have worked through the idea to knock it out.

[Steptoe's photos]

10 hours ago, idosubaru said:

Did you test output in anyway - if installing another pump- run it before connecting the output hose so you can see it coming out and tell if it's muddy from internal tank rust. 

Was the sock on the old pump clogged at all?

If a used fuel pump was installed then there's no telling it's any good. I swapped 3 used fuel pumps in a 1987 XT years ago and all three pumps weren't usable. 

is there even a sock on the external pump to inspect ?

at this stage i would start to check the fpr, maybe just for the fun of it, clamp the return fuel rubber hose for a moment and test drive ? Someone else did this recently and replaced fpr after

[idosubaru]

1 hour ago, Steptoe's photos said:

is there even a sock on the external pump to inspect ?

Yes, if it’s an oem or oem style pump there’s a sock inside the intake line side of the pump.