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one thing that could cause that would be a shorted-to-ground tach wire from the coil (the thinner of the white wires)
easy test is to disconnect it from the coil, then try.

long shot I know, but has come up before on here a couple of times.
 

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Discussion Starter · #62 ·
good you got priorities right, your mum is more important than a car, that's for sure.

I think the relays are probably ok. If pumps come on with the relay, then it, the 8A fuel pump fuse, and the wiring to both pumps is good.

That the big relay makes a buzz is not a great sign, at least shouldn't happen and certainly shouldn't keep on after the key is turned off..........maybe squirt some electrical contact spray (not WD or anything) onto the socket contacts, perhaps there is a dirty contact.

If you got 1000 ohms on each sensor (1.0 on the 20kOhm scale), that is also within specs.
(as Jim G says it is not a guarentee they are good, but it is a first test..............when you get back and have more time, then test them as I suggested above with voltmeter set to AC Volts.....see if you get some signal)

You've now tested and get 12V at the injectors, that's good too.

Your problem is the injectors not being brought to ground to 'fire'.
That might be something simple (like that sensor, or the crumbly connector plug not contacting when you plug it together...check both sides of both connector plugs, that the pins are all there and visible and not pushed back.....remember that black connector sensor is the one that sends the signal to the ECU to pulse the injectors, the upper one)
....but could, unfortunately, also be something big, like the injection ECU has gone bad.


1. what voltage do you have on the negative side of coil to ground? (just key on)
2. have you cleaned the ground bundle on rear of head at the back
View attachment 1690146

btw: keep your battery charged during the tests........this whole system requires 10,5-11,0 volts cranking, or the ECU won't work at all.
Thank You for the ongoing advice. The negative side of the coil has 11v when I touch the multimeter probe to it and the other probe to a ground. I have cleaned the grounds good with electric parts cleaner and made sure they were right.
You say it may be something simple.like the relay. Can the relay still be causing the issue even if I tried bypassing it and the car does the same either way?
 

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Correct me if I am incorrect, the fuel injectors get 12v+ from the relay, and the ground (12v-) is switched by the ECU. So, if when tested, you have 12v+ at the injectors the relay and positive currant path is good. If then the noid light does not illuminate, then either the ECU is not pulsing the ground, or there is a break in the negative currant path. Yes?
 

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If the upper flywheel sensor is bad. The injectors do not get there pulse to fire from the computer.

Its what tells the fuel ecu when to trigger the injectors.

With the connector crumbling apart is one of the signs its failing or going to fail soon.
 

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Discussion Starter · #65 ·
Correct me if I am incorrect, the fuel injectors get 12v+ from the relay, and the ground (12v-) is switched by the ECU. So, if when tested, you have 12v+ at the injectors the relay and positive currant path is good. If then the noid light does not illuminate, then either the ECU is not pulsing the ground, or there is a break in the negative currant path. Yes?
I wish I knew..haha. What really gets me is the car was running just fine until I replaced a slight leaking fuel hose going to the in tank fuel pump. I removed the 4 contacts going to the in tank fuel pump before I removed the leaking hose. I forgot to remove the fuel pump fuse before removing the hose, so I had to quickly put it back on then I removed the fuse. I may have touched wires together I shouldn't have touched or blew something when I was doing all this. Only thing is I ran the car for a minute to see if the hose was still leaking. Next day it would only crank and start for a second then die. It will run on starter fluid sprayed into the intake, but only until it runs out. Feels like I had to blow something like a relay or fuse, or God forbid the fuel ecu.
Is there not any way to check test the fuel ecu to see if I somehow fried it? All this seems strange since it was running and driving fine before the hose replacement.
Thanks again for any and all advice.
 

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Discussion Starter · #66 ·
one thing that could cause that would be a shorted-to-ground tach wire from the coil (the thinner of the white wires)
easy test is to disconnect it from the coil, then try.

long shot I know, but has come up before on here a couple of times.
Thank you. I will try just about anything right now. If I disconnect the thinner of the white wires you are speaking of, what should happen then? What does that test tell me please? Thank you again. This was fun..now it's frustrating..haha.
 

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The only realistic way to test the fuel ecu is to exchange it with a known good one.
 

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If I disconnect the thinner of the white wires you are speaking of, what should happen then? What does that test tell me please?
if you disconnect that white tach wire from the coil and the car starts, it tells you that that wire has a short to ground somewhere along the way.
If removing it makes no difference, put it back as is not the problem.

now, reading your big fuel relay tests over on the 'fuel relay test' thread:

a) you say you are not getting voltage at pin 87 of big drive/fuel relay when cranking? how can that be when you you say when the relay is in place the pumps work when cranking? pin #87 is the output to the pumps when cranking.

b) you say you are getting (editing this, I misread) a little over 12V at pin 30 of drive/fuel relay.....Pin 30 should get full battery voltage as there is nothing in between EXCEPT that 8A troublesome bullet fuse.
So if your battery is showing 12,6 - 12,7V as a healthy battery should (remember 12,1-12,2 volts is only a quarter charged), then that's what you should be seeing at #30, really.
and 11 something volts from pin #15 (KO) also sounds low.
I'd do a thorough check of those two relay sockets and check the wires going to them, that all the pins are securely located, absolutely no signs of burning and then clean, clean, clean:)

The system is very dependant on good cranking voltage.
Those red bullet fuse holders can look great from the outside and can be half melted on the inside.
Most people have long replaced them with a blade fuse holder and 7,5 or 10A blade fuse.
 

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Discussion Starter · #69 ·
I agree
ohming out a sensor is just a first step test (basically if you get 0 Ohms you know they are bust!)

here is how to test them for ohms if you want to just for the heck of it...it's easy enough:

another (imo, a better test, is to test them for signal. Normally you'd do this with an Oscilliscope - yep, I know, we all have one of those in the loft;) - but you can get an idea just with a voltmeter set to AC volts (rather than DC). Set tester to low range 10V AC or 20V AC or something
do the test on the same plug pins as you just did the ohms test (in the snippet jetronic document below) but this time crank over the starter motor......see if you get a signal.....you should perhaps get a reading of 1,5 - 2,0 Volts AC , something like that.

Or, as Jim G says, just buy 2 new sensors, they are old anyway
AutohausAZ does them too (it might not say alfa but PN is correct)
Bosch 0261210002 Crankshaft Position Sensor; At Bell Housing - BMW, Porsche | 12141708619 94460611500 W01331613778
I apologize but I must have checked the larger fuel relay incorrectly the first time. I do get 12.4v out of pin 87. Thank you for catching that for me.

*I get 11.45v from coil to ground.
*I get 3.4 volts AC test (lowest setting I have is 200) on the black flywheel connector when cranking the car. That seems much higher than what you stated it should be. It's the same flywheel connector I got the 1.0 ohm reading on with the earlier test.
*I also removed the small white wire going to negative side of cool to see of it starts, but nothing changes so I connected it back.
*although my horn itself don't actually work, I tried the small cube relay for it and the relay that was in the slot for power windows (which I don't have power windows) in the place for the small fuel relay, but still no change. The car still starts for a second or two then dies.

I know I am being a pain, but I truly am trying here. I'm not just asking questions. If there is anything else I can check, besides just replacing things one at a time, please let me know. I do plan on replacing the black flywheel sensor and pigtail as soon as it comes in.

I can't tell you guys how much I appreciate what your trying to do for me. Am I able to send money or make a donation to the forum? I may not have much left after I finally get this thi g running, but I want to pitch in somehow.
 

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Discussion Starter · #70 ·
if you disconnect that white tach wire from the coil and the car starts, it tells you that that wire has a short to ground somewhere along the way.
If removing it makes no difference, put it back as is not the problem.

now, reading your big fuel relay tests over on the 'fuel relay test' thread:

a) you say you are not getting voltage at pin 87 of big drive/fuel relay when cranking? how can that be when you you say when the relay is in place the pumps work when cranking? pin #87 is the output to the pumps when cranking.

b) you say you are getting (editing this, I misread) a little over 12V at pin 30 of drive/fuel relay.....Pin 30 should get full battery voltage as there is nothing in between EXCEPT that 8A troublesome bullet fuse.
So if your battery is showing 12,6 - 12,7V as a healthy battery should (remember 12,1-12,2 volts is only a quarter charged), then that's what you should be seeing at #30, really.
and 11 something volts from pin #15 (KO) also sounds low.
I'd do a thorough check of those two relay sockets and check the wires going to them, that all the pins are securely located, absolutely no signs of burning and then clean, clean, clean:)

The system is very dependant on good cranking voltage.
Those red bullet fuse holders can look great from the outside and can be half melted on the inside.
Most people have long replaced them with a blade fuse holder and 7,5 or 10A blade fuse.
Just an update: I got the new flywheel sensors in and installed. I am still getting the same issue.
If you don't mind, here is a recap of what I replaced to fix the issue:
*both fuel pumps and fuel filter
*new battery
*new flywheel sensors
Of course I already posted (probably becoming a hassle by now) all the tests I have done. Does it seem to boil down to the fuel ecu? Could the larger fuel relay still be the issue even if bypassing it still doesn't cause it to start? Everything seems to be ok other than the fuel injectors not causing the noid light to pulse or light up.
I really do want to donate or do something for the forum. I was told this was a great group of people, but being on here proved it. Thanks again. Maybe someday I will get it running again and send some pictures.
 

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Did you make sure they are plugged into the same connector. If you reverse them it will not run.
 
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