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XT turbo injectors not firing? SOLVED!!


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35 replies to this topic

#1 joostvdw

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Posted 13 November 2006 - 05:06 AM

I need help, and quickly too, my only and very needed daily driver has quit on me...

it drove fine yesterday, something broke overnight, I have no clue what has happened, I have no other electrical problems or oxidation on ANY plug, so it's not something you would expect.

it's a 1988 XT turbo, MPFI, spider intake, FT4WD 5MT, stock

edit: here's a update, I have found the main problem, the 4 injectors fire 2 by 2, and 1 pair isn't firing, the injectors are fine, there is no signal, I have no pinout's or FSM for my car, so any help on how (and especially where!) to check the wires is appreciated!

#2 Turbone

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Posted 13 November 2006 - 05:37 AM

Sounds like the passenger side timing belt is broke. Remove the cover to find out.

#3 joostvdw

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Posted 13 November 2006 - 06:03 AM

Sounds like the passenger side timing belt is broke. Remove the cover to find out.


no, that's not the case, my bad, I said "distribution is right on" but I meant timing belts :rolleyes: (distributieriem is dutch for timingbelt...)

any way, I found out it only runs on the rear cilinders, the ones facing the front got spark, but they won't fire, so I guess there is no fuel (or injectors don't work)

are the injectors fired batch or single? and if they're batch, in what combination?

edit: yeah it's definately in the injectors, 2 out of 4 are not fireing, but if I switch connectors, the other 2 are fireing, so it's not the injectors themselves who are busted, it's something in the wireing, where to begin :confused:

#4 calebz

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Posted 13 November 2006 - 07:26 AM

Do you have a noid light to test the wiring?

#5 joostvdw

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Posted 13 November 2006 - 07:37 AM

Do you have a noid light to test the wiring?


I don't think so, but I do have a digital multimeter, that should work I guess

but the main thing is, where do I begin? and what could have caused it to die overnight? is there some fuse for the injectors? maybe a resistor or whatever burned out?

testing all the wireing for the injectors from the front to the back (ECU is in the trunk of course) will be a huge task and without a schematic it is going to be even harder.

#6 john in KY

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Posted 13 November 2006 - 07:52 AM

the injectors are batched fired. Don't offhand know if the front 2 cylinders are a pair but check the plug wires at the distributor. If the front 2 cylinders are directly across from each other then they are a pair.
good chance there could be a short in the engine wiring harness. Somewhere in the wiring harness the individual wires from the paired injectors join and become one wire. Hopefully this happens in the engine harness. Identify the wires for the injectors and then unplug the engine harness and check for voltage on the car side of the harness. Offhand I think the CAS in the distributor has something to do with the injectors firing. Don't know if this year used a dropping resistor but that is something else to check. I'll look at the FSM tonight and get back with you.

#7 joostvdw

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Posted 13 November 2006 - 08:17 AM

the injectors are batched fired. Don't offhand know if the front 2 cylinders are a pair but check the plug wires at the distributor. If the front 2 cylinders are directly across from each other then they are a pair.
good chance there could be a short in the engine wiring harness. Somewhere in the wiring harness the individual wires from the paired injectors join and become one wire. Hopefully this happens in the engine harness. Identify the wires for the injectors and then unplug the engine harness and check for voltage on the car side of the harness. Offhand I think the CAS in the distributor has something to do with the injectors firing. Don't know if this year used a dropping resistor but that is something else to check. I'll look at the FSM tonight and get back with you.


thanks for the response, I'll go check the engine harnass, see if there is a short in there somewhere

if this model has a dropping resistor, where should this be located?

and is there any way to check the CAS (crank angle sensor right?)?

If you could post where the connectors are and which wire in this connector is from the injector that would be a great help! then I can locate the short somewhat.

#8 john in KY

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Posted 13 November 2006 - 08:26 AM

Leaving for work but had a thought while shaving. The dropping resistor, if you have one, should be mounted on the passenger-side strut tower.

My thought while shaving was to focus on the dropping resistor. I would think it will have 4 wires, 2 from the ECU and 2 going to the paired injectors. If the ECU side wires check out (Voltage test) then that will tell you just about everything upstream of the dropping resistor is good. Then check the injector wires for continuity. Also check the resistor itself.

Edit: This is what I get for shaving and thinking. Cut myself and got it wrong. Dropping resistor has 5 wires. One is the 12 volt feed wire and the other 4 go to the individual injectors. It is possible 1/2 of the resistor has failed.

#9 grossgary

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Posted 13 November 2006 - 09:59 AM

a noid light will see the injector firing signals which are probably too quick for a multimeter to pick up.
there's spark at each cylinder?
can you swap another ECU?

a noid light might be nice, check signals at injectors (which you already know don't work), at the dropping resistor and finally back to the ECU. somewhere in there you'll narrow it down.

#10 joostvdw

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Posted 13 November 2006 - 10:08 AM

a noid light will see the injector firing signals which are probably too quick for a multimeter to pick up.
there's spark at each cylinder?
can you swap another ECU?

a noid light might be nice, check signals at injectors (which you already know don't work), at the dropping resistor and finally back to the ECU. somewhere in there you'll narrow it down.


I have spark at all four, all four injectors work fine but there is something wrong with the signal

I used a multimeter at the resistor block and measured 1 injector pair slightly over 1V and the other injector pair slightly under 1V, the wires to and from the resistor block seem to be oke, zero resistance, resistor block itself also gives resistance (6 and 12ohms or something, not shorted out anyway)

it seems to me that there is a problem somewhere between the resistorblock and the injectors?

oh and no, I can't swap anything

#11 grossgary

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Posted 13 November 2006 - 10:38 AM

there's no CEL?
if one pair of injectors is over 1 volt and the other is under 1 volt couldn't the issue be there or before the dropping resistor?

continuity and resistance check from the engine harness connector to each resistor might show a wiring issue in the harness.
don't let my responses get in the way of following John's lead, consider mine secondary, he's way good with this stuff.

#12 joostvdw

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Posted 13 November 2006 - 11:37 AM

there's no CEL?
if one pair of injectors is over 1 volt and the other is under 1 volt couldn't the issue be there or before the dropping resistor?

continuity and resistance check from the engine harness connector to each resistor might show a wiring issue in the harness.
don't let my responses get in the way of following John's lead, consider mine secondary, he's way good with this stuff.


nope, no CEL

I'm at a loss at the moment, apparently my car decided over night to disconnect the injectors or something :rolleyes:

the good part about this is that after rummaging through all those wires my central locking system and car alarm fixed it self :-p

#13 grossgary

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Posted 13 November 2006 - 02:09 PM

do you have the wiring diagram? be nice to check the continuity and resistance between the engine harness connector (big one) and injector harness. this will tell you if the harness itself has issues. if you have a multimeter this will only take a minute once you figure out which pins of the connector are for those FI's.

#14 joostvdw

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Posted 13 November 2006 - 05:08 PM

do you have the wiring diagram? be nice to check the continuity and resistance between the engine harness connector (big one) and injector harness. this will tell you if the harness itself has issues. if you have a multimeter this will only take a minute once you figure out which pins of the connector are for those FI's.


yeah I know, IF I had a wiring diagram, I would be able to check continuity, but the only diagram I have is from a USA non-turbo mpfi, so that won't work.

I have checked the dropping resistor, measured some, but none the wiser.

I still think I'm missing something silly, a wire just doesn't snap overnight... and I have NO other electrical problems and no corrosion what soever, so this particular wire, on it's own, causing trouble is unlikely but probable at the same time :rolleyes:

#15 john in KY

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Posted 13 November 2006 - 07:04 PM

Just looked at an 88 FSM, MPFI but not turbo. Don't know if it is the same but who knows. The dropping resistor has 5 wires. The RED wire is the 12 volt feed wire. The other 4 wires go to the individual injectors.

Dropping resistor resistance should fall between 5.8 and 6.5 ohms. Check the 4 wires going to the injectors.

Use a stethoscope to test the injectors. If working you will hear a very audible clicking. The injectors also receive 12 volts. (Another test.)

Back at the ECU, look for a pair of WHITE wires and a pair of WHITE w/Blue stripe. Pin numbers are 49 and 50 for the white pair and 51 and 52 for the other pair. These are the wires from the injectors. Looking for no less than 10 volts.

The dropping resistor is also fused. Doubt if the fuse is the problem but won't hurt to check. Forgot to note which fuse it is.

In an early post you stated something tested at 1 or 2 volts. This can't be. Nothing on this car will work at such low voltages.

#16 daeron

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Posted 14 November 2006 - 12:43 AM

PM me with your email address and I will email you the two .pdf files that contain at least SOME wiring diagrams.. its only part of the FSM for an 89, but it covers SPFI and MPFI engines at least.. about ten megs, so let me know if that is too large for one attachment to your email account.

#17 joostvdw

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Posted 14 November 2006 - 01:52 AM

daeron, I pm'ed you :)

john, thanks a lot! this info will really help, I'll check in the afternoon and bring back results (I hope anyway..)

#18 daeron

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Posted 14 November 2006 - 02:05 AM

email is uploading as I type. I hope its helpful, I have a SPFI NA, so i havent looked thru it for what you need at all... but i KNOW there was SOME MPFI stuff in there.. GD said there was some of it missing though. it should be of help, open part 2 first, that has what you need.

#19 joostvdw

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Posted 14 November 2006 - 08:36 AM

email is uploading as I type. I hope its helpful, I have a SPFI NA, so i havent looked thru it for what you need at all... but i KNOW there was SOME MPFI stuff in there.. GD said there was some of it missing though. it should be of help, open part 2 first, that has what you need.


thanks, I got them!

with the help from john and daeron here, I managed to locate the problem to a faulty wire somewhere between the engine harnass and the ECU, the problem is however that I can't find a plug a long the way, so I don't know exactly where the problem is and replacing the whole wire is, well, a bit "uncivilized"...

#20 calebz

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Posted 15 November 2006 - 12:56 AM

thanks, I got them!

with the help from john and daeron here, I managed to locate the problem to a faulty wire somewhere between the engine harnass and the ECU, the problem is however that I can't find a plug a long the way, so I don't know exactly where the problem is and replacing the whole wire is, well, a bit "uncivilized"...


Uncivilized hell.

Trace it back to where the signal is good, hack the bad chunk out. a little twisting, some solder and a bit of shrink wrap and you're good to go :)

#21 daeron

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Posted 15 November 2006 - 02:52 AM

Uncivilized hell.

Trace it back to where the signal is good, hack the bad chunk out. a little twisting, some solder and a bit of shrink wrap and you're good to go :)


he is right. just patch something in, and confirm that you are right. then break your skull on making it pretty later. make it good and functional, but all you have to do is cut out the nasty bit and stitch it back together.

#22 joostvdw

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Posted 15 November 2006 - 12:33 PM

so, I'm a little further now, I ran a long wire directly from the ECU to the main engine harnass connector (the big one) and that fixed 1 injector, I then made a small jumper wire out of 2 needles and a length of normal gauge wire, connected the not working injector to his partner on the other side and voila 4 cilinders :banana:

I'm probably going to run completely new wires, front to back, with new connectors on the injectors, so that I don't have to cut anything and check if that fixes my problem

only thing is, where to get these connectors? anyone know of cars that use the same injector connector? I guess maybe a nissan?

#23 daeron

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Posted 15 November 2006 - 08:39 PM

My car is SPFI, but if they are the standard bosch Fuel Injector Connectors, many many many cars. VW, Audi, M-B, BMW, alot of american brands too, jaguar i think... A LOT!!! shouldn't be too difficult, presuming they have junkyards over there in.. Holland.. :) Even if not, you can buy them new.

Clicky for a catalog image of the connector I am talking about.

#24 joostvdw

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Posted 17 November 2006 - 11:42 AM

alright, I replaced the wires going from the malfunctioning injector back to the ECU, all of them, from the front to the back,

it was a terrible nightmare to strip the entire interior to route the cables somewhat besides the original wire loom, soldering upside down in the trunk, a lot of swearing and cursing

and you know what? it still doesn't run properly. sometimes 3 cilinders, sometimes 4, and just now, it didn't even start (trying to run on 1)

#25 grossgary

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Posted 17 November 2006 - 11:58 AM

AH! that's crazy. so you ruled out the wiring harness completely it sounds like?

too bad you don't have a dropping resistor and or ECU to swap. i have a couple ECU's one or two are turbo's.....you want to post the part number of your ECU?




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