cam.in.head

Strange one

15 posts in this topic

My 76 cav fitted with 2.2 setup did a strange thing the other day. Conversion done in 2005 run fine ever since with no issues except one which I will tell you about in a minute.went out weds night.all running fine.car suddenly died so pulled up and was turning over fine but no sign of firing.poweered up fuel pump fuse and could hear pump running,tried to start still nothing.checked for spark with engine spinning ,perfect,coil centre lead to block .rotor arm and cap and leads all fine.replaced pump relay.no difference.tried a few more times.nothing.rang my mate with a towball.he came up and we tried it first and car fired up and ran perfect for all of 30seconds then stopped suddenly again.we towed car to outside my house then removed tow rope.he moved his car out of the way so we could push my car into my garden tried my car,it fired up again and drove into my garden where it stopped again and wold not restart.in the morning I came out and tried it,started up and ran perfect for 2 hours,went for a drive,perfect,been perfect ever since.now this is a situation we all hate. There is a loose wire,connection or component somewhere that may last 1 more minute or never occur again ever!.i have checked every connection and wiggled whilst running,measured correct voltages to pump relay socket main live,term50 term 15 all live as required.earth present at 31.will be carrying my meter ,spare relay and some wire with me for a while now.going to check inside Ecu plug and make sure earth is present there with no undue resistance.i have a spare of everything including loom and am almost tempted to replace everything! !.this is one of those stupid annoying faults. Anyone have any more advice if they have ever suffered similar.                     Other issue which it has always done and I've never been able to get to the bottom of is this.the car will idle fine at say 600 for ages then occasionally the revs will drop to a steady and sudden 500 for approx 10 seconds and stay there all smooth.then return to 600 again for no reason.nothing switched on or off.i have tried different main Ecu,idle Ecu,icv,ignition module,coil,in advance module etc all no difference and from another know ok car.the fault even happens with the icv unplugged ! And also with the throttle switch unplugged,tried different fuel pump and relay too. It has done this since fitting in 2005 and never gives any issues but what the he'll is it ? . Could it be a pressure valve opening and closing in the auto gearbox ? ?...could these issues be related ?.thanks to all who may read this.sorry it's a long description.cheers Chris.

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I had a very similar thing with a bmw e46, drive me mad. Would just cut out on motorways etc, then work fine after 3-20 mins. Changed everything, no ryhme or reason. Gave up and sold it on

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this is why problems like this are so annoying.no intension of ever selling car so fault must be found .but WHERE ? . its obviously something somewhere and i will work my way through everything until i find something or until it does it again then test for lost voltages

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It defo sounds like a "connection" issue. If you hadn't of changed your coil I would have said look at the colour of your spark when you pull the plug out to check for a spark. It sounds like a Coil breakdown. When you've got your head under the bonnet it's fine but under load it fails, also the fact if you leave it it works is interesting and pertains to a coil issue.

I have taken a lot of wires off my manta loom that were very stiff and brittle. This is meaning the insulation is on the way out and when we check the copper on these wires we find they it will have corroded a long way back.

If you have changed everything else then  something in the loom sounds suspect. If you have a spare loom get it out flat on the ground untape back for any connections (especially under bonnet connections) and inspect it very closely replace anything that is stiff back to good wire . I have replaced a loom before and I took about a day

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Hi .thanks for the suggestions. Yes I have a spare injection loom both for the engine side and the spark advance side of things. Did some more checking today.opened up the Ecu plug and examined every terminal/wire and pushed and pulled them all when running. No obvious issues at that end.earth continuity perfect.zero ohms to body full voltage to Ecu as well..did same to idle control Ecu also put on a brand new main Ecu,idle Ecu and a different spark advance Ecu.checked when running all terminals in pump relay plug and swapped relay as well.already done this once anyway.the car has never missed a beat since starting it the morning after and I've found not a single bad or even slightly suspect connection.re wired the ign '15' feed to the pump relay and to the ign module and coil.all new bougicord original hit leads.all I can do now is carry meter in car until it does it again and then il make sure voltages are still appearing where they should be.with pump relay removed term 30,87 & 87b make it run so il confirm that too. It's just one of those stupid annoying faults that will either never happen again or turn out to be something obvious eventually !

Edited by cam.in.head

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Good luck with it, let us know If you find the fault

Edited by The General

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Try 2p Trick when problem in evidence

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10 hours ago, mantadoc said:

Try 2p Trick when problem in evidence

What's the 2p trick?

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2p trick won't work on mine as its a 1976 cavalier. The pump is fitted with an inline fuse looped through fuse box but not no7. If it does it again I will just link 30,87 & 87b on relay base.

3 minutes ago, The General said:

What's the 2p trick?

Linking fuel pump fuse in fuse box to next fuse with a 2p piece.in other words sending 12v direct to pump avoiding any relay issues.obviously this only powers pump to prove pump works and doesn't  make the injector common live too.hence why I'm going to just link the pump relay socket if it does it again

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Just remember that bridging the relay fuel pump contacts on the base with the relay removed stops a running car running - the relay needs to be in the socket if we are talking about the fuel pump relay with all the extra little contacts

35 minutes ago, The General said:

What's the 2p trick?

An example of my awesomeness ;)

 

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Why does it stop a car running. It doesn't on both of mine.they are both standard 2.2setups. The relay surely supplies power to the pump(term 87b) and power to injectors common(term 87) from the permanent unfused live at term 30.it starts the sequence when a live is applied to term15 and cranking to term 50 followed by a coil switching detection to term 1.and keeps this going until either it loses coil switching or looses term 15 / ignition turned off. This is what mine does or are the 2 litre versions different. I know some say the 2 litres have a 2 sec fuel prime whereas the 2.2 don't. 

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Have you tried replacing the airbox? I had a similar problem years ago on mine. Turned out that the fingers that run on the tracks in the top of the airbox had worn through for some reason. That seemed to throw the ecu into fits and the car would just die, and then fire up again later. Changed the airbox and everything was fine. Other thing to check, 3 pin dizzy connector.  The wires were/are prone to breaking down with age so check there for any problems.

Hth

Chris 

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Ignition amplifier is a good one for this issue. Over heats cuts out cools  runs great again. Had this a few times. 

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Thanks for all suggestions will change ign amp and coil. Will also carry a different air box with me too.

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