New problem with my 450

[koan]

I tried to test with test lamp today without any result at all at any of the injectors. Does the engine have to be running?

Yes

i will try to switch them if i dont get this test lamp thing to work

Forget the test lamp, just swap the injectors and do the compression test again.

koan

[oscar]

Ditto.   

[Bulba]

Okey, i will do that then. I will hit you up with the results later. Can take some time though, because i have to borrow my friends compression tester and he lives kinda far away and i dont know when he comes to town next time.

[Bulba]

Havent got hold of the compression tester yet.... But this evening my steph dad checked everything, and when he opened upp the ECU he noticed that one contact was pretty loose. So we cleaned it up and put it back properly. But then when we was going to test start we saw that the thread in one of the holes for the spark plug was broken so now i have to find some thread-tool with the same thread as a spark plug to fix it. Then we can test start, and maybe the loose contact is the problem, who knows?

[Bulba]

Now the compression test is made, and it still has the same results as the first time even though changed injectors. SO i guess the ECU is the problem!

[TJ 450]

If you have ensured that all contacts are clean and that the wiring to the suspect injector is 100% functional, then I would suspect ECU as a possible source of the problem. You should also ensure that all ground connections are showing minimal resistance too, if you haven't already.

Tim

[koan]

Now the compression test is made, and it still has the same results as the first time even though changed injectors. SO i guess the ECU is the problem!

So you swapped the injectors around and still have 17 bar on number 4 cylinder, yes?

Did you by any chance do the compression test on number 4 with the injector disconnected?

I still have a bit of a doubt that the ECU is the problem. Looking at a 4 cylinder ECU circuit, pairs of injectors are driven by a single output transistor but via individual resistors. Assuming a 6 cylinder ECU has three output stages, each one driving a pair of injectors via individual resistors I don't see how one injector and not two can be turned on all the time. One of the single resistors going open circuit would stop the associated injector working, not turn it on constantly.

If it is really the ECU the problem would have to be one of the six large output resistors or the associated wiring, a short circuit to 12V for instance.

Before spending money on an ECU it might be a good idea to do what oscar suggested with the test lamp. Try to organise some way of connecting a 12 V lamp across number 4 injector and see if it lights constantly or flashes, an instrument panel lamp would be ideal.

koan

[Bulba]

i have found a spare parts car now. The only problem is how im gonna get it home, it runs but its not safe to drive due to old hoses and bad brakes. If i cant get this home in some way, i will try what you said koan!

[Bulba]

I have found a way to get it home now! So hopefully i can go get it this saturday or something like that. So now i got the ECU and the injectors

[oscar]

Good stuff bulba   Sounds like you've got a busy weekend up ahead. I want to see that 450 flying by Monday

[Bulba]

As always, its a new bump in the road. Not so big one though. The car trailer was broken, some electrical faults and stuff. But it will be fixed until after christmas, and then the new car arrives, hopefully.

[Bulba]

The other car is here, ive changed the ECU and the injectors, now it doesent mix fuel in the oil anymore =) But now there is a new problem ofcourse, it wont start at all, wont even ignite (dont know what its called in english). Any ideas guys?

[Niclas]

Well try to change back the ECU. Then you can identify if the other cars ECU is foulty. Maybe some of the little copper contacts in the 24 pice contact harness got bent?? Another idea is that you have got some oxidation on the breaker contacts.

/Niclas

[Bulba]

Changed the ECU back, still nothing. Checked the contacts, nothing bent or anything. WHere is the breaker contacts located?

[13B]

In the side of the distributor.