help me diagnose the ECU problem...

72RSbug · Post by **72RSbug** » Tue Jun 26, 2007 3:00 am

stock JDM EJ20TT engine+ECU

engine only fires up when I put a negative wire on the ECU relay to activate it (the one coming from the ECU doesn't do it).
-> the engine turns over because of the starter and the sparkplugs fire but the ECU doesn't activate the fuel pump relay

I can get it to keep running for about a second or 10 when I put power directly to the fuel pump but it seems the mixtire is all wrong and it misfires.

I've checked the wiring and the ECU gets the power it should to work but the only signal it sends out (as far as I can tell) is spark plug fire.

Have tried with a different stock ECU and it's exactly the same story.

Any ideas anyone?

also important: part of the wiring loom (that leads to cam sensor among others) got fried against a turbo. I replaced all these and had to replace the ECU relay also.

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Tue Jun 26, 2007 11:39 am

Are you sure the cam belt hasnt jumped?

Outback bloke · Post by **Outback bloke** » Tue Jun 26, 2007 5:21 pm

Is the harness intact? Or has it been stripped down to fit in your car?

72RSbug · Post by **72RSbug** » Tue Jun 26, 2007 8:54 pm

the harness had been stripped down before I bought it to fit my car (VW Bub), but I've driven it with the TT engine in it for about 6 weeks before the loom got fried.
Might be a good idea about the timing belt, I'll make sure to check it(but if it jumped, would the ECU only give out a signal to the spark plugs and not to the engine or fuel pump relay like it does now?)

Matatak · Post by **Matatak** » Tue Jun 26, 2007 9:30 pm

and the fuel pump relay is ok? seen as thats wt u have to bypass for the fuel to start pulsing.

when uve acually had it running does it kill itself off after or do u only keep it running for like 10 secs

72RSbug · Post by **72RSbug** » Tue Jun 26, 2007 11:14 pm

the fuel pump relay works.

Either the engine will misfire or I just stop it because of the fuel that comes through the primary turbo (very dangerous in the exhaust)

Matatak · Post by **Matatak** » Tue Jun 26, 2007 11:43 pm

does sound like timing problems if its doing that.
i suppose ull have to check the belt to actually see if everything lines up when its "supposed" to be on TDC

72RSbug · Post by **72RSbug** » Wed Jun 27, 2007 12:03 am

I'll check out the timing belt postion tonight. Should be that all the markers on the pullys line up with the markers on the engine, right?

Matatak · Post by **Matatak** » Wed Jun 27, 2007 12:13 am

well ive never seen a TT of a Subi but if you have a book it should describe it.
they should have marks on somewhere neway that lign up with others.
manufacturers are all different but for my dads outback DOHC EJ25 the top two cam pulleys line up with a mark on the rear timing covers at the top then they have a double line at bottom which lines up with a double line on the the other cam pulley on saem head.

72RSbug · Post by **72RSbug** » Wed Jun 27, 2007 3:56 am

Just got home and checked the timing belt and it seems to indeed be off

the single marker on both upper cams line up with the marker on the timing belt cover but the double marker on upper and lower cams do not (pics)

Matatak · Post by **Matatak** » Wed Jun 27, 2007 7:39 pm

well theres a problem there then.
they do seem to be a dodgy thing and have to get the single lines axactly right as it can look right and make the double lines apart but then if you get the double lines together sometimes the singles will still line up

72RSbug · Post by **72RSbug** » Wed Jun 27, 2007 8:22 pm

ordered a new belt and wil put that on this weekend.

is it possible this is the cause of the ecu not giving a signal to the fuel pump relay and the brown ecu?
seems to be a long shot to me.

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Wed Jun 27, 2007 10:09 pm

Those pics of the cam timing look ok. Do you have power going to the fuel relay in a start pulse?

steptoe · Post by **steptoe** » Wed Jun 27, 2007 10:24 pm

and you have a twin turbo in a VW bug ??

72RSbug · Post by **72RSbug** » Wed Jun 27, 2007 10:34 pm

Those pics of the cam timing look ok

really? the double marker is not alligned on both cams, is this the way it's supposed to be?

Do you have power going to the fuel relay in a start pulse?

nope, ecu does't give any signal to the fuel pump what so ever.

and you have a twin turbo in a VW bug ??

yes, Subaru engines are a lot cheaper then high HP VW type 1 or type 4 engines and should be more relyable. Makes for a wild ride in a 650kg Bug

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Thu Jun 28, 2007 9:41 pm

Yeah one side will look pretty much right the other side (drivers) will look a tooth out so looking at those pics that looks correct. The top cam wheel has the sensor so as long as it is in the correct cycle it should start. Next Q Are the Cam and crank sensors plugged into the correct places, ie you havent got cam into crank etc?