1987 3.2 Carrera Backdate project - Sladeys hotrod

[sladey]

I’ll try a spark plug tomorrow, but given how much it has been cranking there is no smell of fuel at all.

It won’t be easy to check out that plug but I’ll see what I can do

I’ll also see what I can do about running tests on the sensors


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[rhd racer]

From my experience;

1. Jump the DME (jumper lead with 3 male spade connectors)
2. Crank sensor - I don’t know why, but these seem to be made of chocolate these days and I have replaced two within 1k miles
3. Disconnect the ECU and reconnect. I had mine not play a tune for ages and the clamp that draws the connector home was open by about 5mm, which was enough to make the fuel circuit not live (it is one of the last connections on the top row of the ECU). Felt like a berk….
4. Tap the fuel pump with a hammer as they seize after lack of use, and again some brands can be super unreliable. I think I have a spare 964 one if you need it as I suspect the same

HTH - good luck


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[sladey]

Thanks Wayne and Jon and Gary

OK I’m trying to read this wiring diagram to help me work out how to test that plug wiring works

https://ensaster.com/pics/pelican/diagr ... iagram.pdf

The top one is black and white and the bottom is the same one in colour.

Looking at the wiring leading from the fuel injectors, each bank end up with red wires all connecting into a box marked “2” - what is this? Is it an earth?

I’m thinking that the connections around co-ordinates F43 represent the plug I might have damaged. From that I’m thinking that the two red wires go to earth and the other two wires go to connections on the plug going into the ECU - connections number 14 and 15.

So I’m thinking I could run a continuity test from connections 14 and 15 to those two pins, and (If I’m right that 2 is an earth) run a continuity test from the other two pins to a good earth.

If I’m getting continuity on those 4 connections then the plug should be OK

Is my logic right on this?


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[rhd racer]

If the 3.2 is the same as the 964 it is not so easy to identify the wires in that connector block by colour as one of the sensors is a 993 part and changed colour. I can’t recall what the 3rd is, but one is CPS, I think the other cylinder head temp sensor for cold cranking I think. I’ve replaced both sensors in the past when all else seemed to fail and my instinct is that as you say you damaged the connector or one of the sensors has gone West. Am struggling a bit to follow the diagram on my phone I’m afraid but my experience of bad sensors has led me to replace them


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[rhd racer]

One other thought - isn’t it the cylinder head sensor that you loctited in? Any chance of contamination on the tip of the sensor?


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[sladey]

I’m confident there is no loctite on the tip of the cts sensor but in any event that isn’t touching anything - it doesn’t bottom out in the hole

But anyway I don’t think the cts would stop it from starting - I’ve had a faulty cts sensor before and it started fine but ran badly

[Bruce M]

Wiring diagram is useful.

Injectors work by a continuous 12v feed and a ground side switch by the ECU.
The connector you mentioned, is for the injectors. Pins 1 & 2 are the solid 12V feed, via a common point marked [2] on the diagram, being fed from pin 87 on the master relay.

Pins 5 & 6 on that connector are the ground switch wires that go back to the ECU.

The injector are fired in 2 batches of 3, so to check the connector is sound, you only need to test 2 injectors connectors with a multi meter.

[sladey]

Thanks Bruce that’s really helpful and cleared up what the 2 is

What’s occurred to me overnight is that I checked the socket in the engine bay and it looked fine and clicked back together. However I never looked inside the male plug that was attached to the intake stuff

So today the plan of action is:-

1. Carry out test on DME relay to confirm that is working using tests in Bentley manual
2. Carry out test on sensors to confirm they are working using tests in Bentley manual

Provided 1 and 2 are OK then
3 remove the intake manifold - should just be the barrel nuts, the fuel feed and return and a few other pipes and connectors. Then I will have full access to the plug, and also (not great) access to the socket it plugs into - at that point I may come back with further questions about what I’m trying to test if I can’t work it out from the wiring diagram

And if you have trouble looking at the wiring diagram on the phone here is a screenshot of just the relevant part



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[Bruce M]

Bit of info on the relay.
It has two stages. Stage 1 powers the injectors with 12V plus a couple of other components (idle valve etc). Stage 1 is controlled by a 12v feed from the alarm. Stage 1 output also provides the 12V power to stage 2 solenoid which is activated by an earth side switch by the ECU. Stage 2 powers the fuel pump & the O2 sensor.

Id suggest this as your first test to baseline.

Disconnect an injector plug. Earth your multimeter to the engine block. With the ignition on, check the two pins on the plug & one should give you 12V. That will confirm the live feed is working & the relay /stage 1 is powered. Then keep the Red multimeter probe on the same pin & connect the black meter probe to the other pin (you might need to use a bit of wire). Be very careful not the short the pins. With an assistant cranking the starter, you should get flickering voltage across the pins as the ECU earths the other pin. Ideally if your meter has “duty cycle” or “dwell” use that because the ECU is earthing for short cycles.

If the first test doesn’t work, you have a problem with the power feed to the injectors. (Check one more injector to confirm the other bank).
If the second test fails the ECU is not firing the injectors for some reason or the connector is broken.

[sladey]

Fantastic - thanks Bruce

[sladey]

OK I’ve tried that now

I first did the tests on the DME relay and they seem to be working fine - pin 87 is charged up with 12 volts.

Then I went to do your test on the injector plug. Tested the first pin and got 12 volts. tested the second pin and got 12 volts again! Not sure what that means.

I tried it on injector 4 and then did the same on injector 1 with the same result


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[sladey]

Then I did the tests in the Bentley manual on the two crank sensors - position sensor and speed sensor. Pins 1-2 are meant to give 960 ohms resistant and 1-3 and 2-3 area meant to give over 100K

1-2 tested fine on both plugs and came out around the 960 mark

1-3 and 2-3 - I couldn’t get a reading no matter what I switched the tester to - it just said 1 each time. this is the first time I’ve ever tested resistance but as I tested every range (200,2K,20K,200K, 2000k, 20m) I can’t see what i could have done differently.

I’m assuming these are OK though. I didn’t touch them during the work and they haven’t given any trouble for years

OK so on to removing the induction system


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[Gary71]

Sorry if I missed this further up the thread but basic questions sometimes are the best.

1. Is there fuel in the tank?
2. Is the fuel pump running?
3. Is power getting to the ECU?

[sladey]

No harm in asking

The tank is fairly low but there is fuel there - there was fuel pressure built up in the fuel filter when I loosened the fittings

the fuel pump is running - I can hear it each time

I believe power is getting to the ECU but haven’t tested that - I did test that power was getting from the DME relay to the injectors. I’ve no reason to suspect power isn’t getting to the ECU - I haven’t touched it


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[RobFrost]

First off, check all connectors are well-seated and retry starting. Then check all fuses, especially fuel system and ecu. Then fill a petrol can and empty the contents into the tank, and retry. Confirm that you checked spark on the plug lead not on the centre lead. Confirm that you earthed your timing light to the engine and not to the body. Assuming that doesnt work:

If you have spark then you either don't have compression, fuel or timing. Let's assume you've got compression. Did the crankshaft come off, and if so, did it go back on with the tdc mark in the same position? If it didn't, replace crankshaft in correct orientation!

To check if it's fuel, spray carb cleaner or a little petrol in the intake while cranking. If it fires, you're probably lacking fuel.

I'll assume that's the case. Either add a fuel pressure sensor to the rail, or loosen the test port slightly (with a fire extinguisher on hand) and confirm fuel comes out while cranking. If not, it's probably not pumping. Can you hear it? If not, bridge live power to the fuel pump in in the fuse box and confirm it makes the fuel pump run. If it doesn't, then do the same again many times on and off, and see if that will free the pump. You will hear it turn.

Now suppose instead you did have fuel pressure. If you have a scope or an AC setting on your multimeter, scope the terminals to an injector while cranking. Confirm you get one pulse per two revolutions of the engine. If you do, your injectors are receiving their signal. If not, they're probably not. Confirm by removing an injector and watching for fuel while cranking (with an extinguisher on had). Check connectors between them and your ecu.

If you have fuel, compression and spark then timing must be off. Check spark timing with a timing light while cranking.