eaglescout526

You can test for resistance and voltage and see if theres a drop.

Ah makes sense. Well he needs to make a build thread for us to watch.

Ok so that was splice "K" to EGR then FI then runs to the D1_6 in that mess and to another splice probably hidden in that mess. I am willing to bet the black splice is a ground, maybe like the CTS and ATS sensors ground, they do share a ground and splice in wire color brown with tracer. Then theres two other ground wires from the ECU that go into a splice that go to G110 and D2_7 on a black wire.

Crap there was also that one other member down at South Mountain, forget his username though. But may I ask what says it is him?

First splice should go from 87(one wire) to the splice which branches off four time, one to the EGR, one to the FI, one to D1_6 and one to C113. Then from C113 an orange wire goes to another splice of five more orange wires with a connector going nowhere and four going else where and to C100(bulkhead connector) But the second splice should be orange wires, not black so I am not sure about that second splice. I can't seem to find C114 in the schematics but it isn't under engine control. Do both connectors have an orange wire or just the one? If just the one that is the C113

So according to the schematic, from 87 on the relay, it goes to a splice, then from the splice it goes to the fuel injector, EGR solenoid and Connector 113 which is a four prong plug. There is also a C114 which looks identical to C113 but C113 should have an orange wire that leads to a splice that feeds a load swap relay, PS switch and to C100 which is the bulkhead under the clutch master cylinder, then from there it goes through the cab to the fuel pump connector.

Like I was saying early on, between the relay is two splices and two connecters. One of those could be corroded enough to cause issues.

Sure, lets see what happens. I wonder if theres something from the relay to the pump that would cause such a drop.

Is this with relay in socket?

Should be around 12V.

Yep, continuity is a constant tone, if you were to touch your probes together, it will beep until you stop having them touch. We have tested everything and so far everything works except the fuel pump prime, pump during crank and the ISA motor. I'm not sure what else to check and test.

So it looks like the ECU is trying to extend it for warm up sequence. That was a good capture, probably wouldn't have seen the numbers. Alright that's enough of the ISA. Well do we want to look at the B+ circuit? 85 goes to T7 and to D2 but the schematic doesn't say. 87 goes to D2_4(swear it should go somewhere other than there) and 86 goes to T19, so we can check for continuity.

Ok, we might have to try the ground probe in D2_7 rather than D1_3.

Upon shut down of the engine, was there a voltage increase at D2_11 for the extend? If you happened to observe that?

Well it is entirely possible the ECU isn't extending the ISA like it should, we will have to test voltage to see if the ECU is extending it or retracting. D2_11 is extend, D2_14 is retract and D1_3 is the ground. Which mean we will have to do another fuel down the TB test and observe extend on one start up and retract on another, we will be looking for voltage greater than our baseline. I am willing to bet the ECU is trying to extend it.

Thank ya! Shame, ISA motor might be chunked, but we ruled out a completely closed throttle being a problem. But we still don't have the fuel pump running when cranking with the relay.

Sounds good and will do!

SatiricalHen is going to a salvage yard tomorrow for some cruise control stuff, he says he knows where an 86 2.5L is, so he said he will snag the ECU from it. Id pretty much go through the wiring before you drop in a new ECU just to prevent the same issue from happening to a new to you or reman ECU. I mean I still think it is something in the fuel pump circuit but we are running low of things to test. You should pour some fuel down the TB tomorrow and see if the ISA will function after shut down.

I meant on the B+ relay, pin 30 on both relays should go right into a fusible link. This is tons of fun!

Yeah the book shows you how to locate it and remove it. I am not sure what would happen if we jumped the 30 to the 87 though.

Check the B+ relay. Check the wire harness and connectors, repair or replace as necessary. But the possible cause of the B+ would be no battery voltage applied to the injector(12V from one pin to the chassis ground). That's what the book says, but nothing on how to test it.

Theres nothing on the starter relay to test....I wonder why the book would say to look there. I just looked at the electrical schematics for the relay and fusible links and only saw the one fusible link for the ECU, FP relay and B+ relay. So theres nothing on the starter relay to give power to.

Yes I am.

No its not saying to have a wire go to the FP relay, but on the starter relay is also a terminal that triggers the fuel pump to run during start up. I do not know which terminal that is.

Ok so no trouble with that circuit. So the relay should energize, still not sure why it won't do the prime sequence.