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Apr 10, 2019 20:53:07 GMT
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My son has a 1983 Opel Monza 3.0 Coupe with fuel injection, it had been off the road for many years & has only done about 1000 miles since, the car started to stall & has got worse, now it will start from cold, the revs will rise & fall about once a second then after a minute or two it will stall & not restart although it tries to catch. We have had the fuel tank out & replaced the vent hoses & the hose from tank to pump, the pump looks new, the fuel filter has been discarded by a previous owner & bypassed, we cleaned the air idle valve & the mass air flow sensor with carb cleaner, & now we are scratching our heads. I wondered if the fuel pump relay is at fault, we can hear the pump running when the starter is turning over but I have heard that the relay can interrupt supply when it gets warm if it is faulty, what do others think?
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mk2cossie
Club Retro Rides Member
Posts: 2,948 
Club RR Member Number: 77
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Stalling Opel Monzamk2cossie
@mk2cossie
Club Retro Rides Member 77
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Apr 11, 2019 19:02:18 GMT
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Has it got any kind of filter for the fuel at all? If not, there could be all kinds of crud behind the injectors if it has been stood around for a while  My first port of call would be to try and get the fuel system clean and a filter installed and go from there  |
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Apr 11, 2019 19:55:02 GMT
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No filter & it was used for film work before we got it, lots of cop chases, treated a bit rough. the tank is newish & very clean inside.
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mk2cossie
Club Retro Rides Member
Posts: 2,948
Club RR Member Number: 77
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Stalling Opel Monzamk2cossie
@mk2cossie
Club Retro Rides Member 77
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Apr 11, 2019 21:02:54 GMT
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The tank may be, but was it filled from Jerry cans on set? If so, there may have been all kinds of curse word in those not filtered out  |
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Apr 11, 2019 21:16:33 GMT
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Does it run K-jet ?
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Needs a bigger hammer mate.......
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Apr 11, 2019 22:41:11 GMT
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I had a very similar fault many years ago on one of my Monzas.
I’m sure you are aware of of the Achilles heal on the Monza was water ingress from the bottom of the windscreen on the drivers side running or dripping down into the footwell panel where the ECU is located which incidentally faces up with the cable acting like a flow guide for the water to ingress inside the ECU. More importantly above the injection ECU is the idle control ECU which is a smaller black box that clearly could cause the issues you are suffering. This is a bit more difficult to get too but I would put money on this being faulty. Derek at GM6 in Cornwall is your man for this.
It doesn’t take a lot for this to cause havoc and all sorts of gremlins. I solved this by replacing the ECU (Both) and instantly worked. Different Monza model variations have coloured stickers on them, eg manual with air con, auto without air con etc.
Another similar issue on a different Monza was the electric feed to the fuel pump intermittently cutting, that being said this fault would simply stall the engine and as such never run lumpy. I had to bypass the wiring to fix that.
On the point of a fuel filter, this is a simple cheap addition and it should really have one so you may find your injectors are clogged up, they were never the best design.
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Last Edit: Apr 11, 2019 22:52:27 GMT by hotfuzz
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What is K-jet, 1980's stuff is a bit modern to me. |
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Bosch K-Jetronic fuel injection system.
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Phil H
Posted a lot
Posts: 1,448
Club RR Member Number: 133
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Stalling Opel MonzaPhil H
@philhoward
Club Retro Rides Member 133
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Apr 12, 2019 16:26:34 GMT
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I thought a Monza runs L-Jetronic?
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Apr 12, 2019 16:52:04 GMT
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I thought a Monza runs L-Jetronic? My Senator 24v on an L reg ran L Jetronic. Following this with interest as got similar problems. |
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Last Edit: Apr 12, 2019 16:53:57 GMT by v8brick
"To Big block or not to Big block?" Thats the question!
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Phil H
Posted a lot
Posts: 1,448
Club RR Member Number: 133
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Stalling Opel MonzaPhil H
@philhoward
Club Retro Rides Member 133
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Apr 12, 2019 20:03:35 GMT
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If it has a separate cold start valve (a seventh injector), they can be a problem but I think that was only on very early L-Jet stuff.
If the idle speed is surging, then the question is whether it’s the ECU doing it trying to prevent stalling (badly), or it’s doing it because of strange readings it is receiving.
Need a couple of pics of the inlet manifold area to guess further..
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Apr 12, 2019 20:28:55 GMT
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It's my son's car, will try to find out more when I next see him.
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No filter & it was used for film work before we got it, lots of cop chases, treated a bit rough. the tank is newish & very clean inside. Was it this one prior to the black wrap being taken off? As driven by The Hoff!  |
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Last Edit: Apr 13, 2019 2:51:04 GMT by hotfuzz
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Apr 13, 2019 17:06:53 GMT
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Apr 16, 2019 20:41:07 GMT
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I had a very similar fault many years ago on one of my Monzas. I’m sure you are aware of of the Achilles heal on the Monza was water ingress from the bottom of the windscreen on the drivers side running or dripping down into the footwell panel where the ECU is located which incidentally faces up with the cable acting like a flow guide for the water to ingress inside the ECU. More importantly above the injection ECU is the idle control ECU which is a smaller black box that clearly could cause the issues you are suffering. This is a bit more difficult to get too but I would put money on this being faulty. Derek at GM6 in Cornwall is your man for this. It doesn’t take a lot for this to cause havoc and all sorts of gremlins. I solved this by replacing the ECU (Both) and instantly worked. Different Monza model variations have coloured stickers on them, eg manual with air con, auto without air con etc. Another similar issue on a different Monza was the electric feed to the fuel pump intermittently cutting, that being said this fault would simply stall the engine and as such never run lumpy. I had to bypass the wiring to fix that. On the point of a fuel filter, this is a simple cheap addition and it should really have one so you may find your injectors are clogged up, they were never the best design. I believe that the idle control ecu is behind a bit of duct, I remember that when my son got the car there was a bit of plastic duct loose in the car, we never got around to finding out where it went so may be someone has been at the idle control ecu before. He did get a little bit of water drip on his feet once. |
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Apr 26, 2019 10:48:49 GMT
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Just an update, my son found that the loose bit of duct was the one in way of the ECU’s, the trim was loose, & when he removed it he found that the larger ECU was attached by one screw instead of four, the smaller ECU was not attached at all, just propped there & both were wrapped in a plastic bag so someone has been there before. He cleaned the connections with an electrical cleaner, but both ECU’s were dry after a week of hot weather, he topped up the petrol tank from a can as the gauge was near the empty & the car started & ran without surging or stalling, he could not road test it as it is out of MoT, so now we have to trace the water ingress, where do they leak, windscreen, sun roof drain?
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Apr 26, 2019 12:41:39 GMT
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Just an update, my son found that the loose bit of duct was the one in way of the ECU’s, the trim was loose, & when he removed it he found that the larger ECU was attached by one screw instead of four, the smaller ECU was not attached at all, just propped there & both were wrapped in a plastic bag so someone has been there before. He cleaned the connections with an electrical cleaner, but both ECU’s were dry after a week of hot weather, he topped up the petrol tank from a can as the gauge was near the empty & the car started & ran without surging or stalling, he could not road test it as it is out of MoT, so now we have to trace the water ingress, where do they leak, windscreen, sun roof drain? I hope that your son has rectified it however if it has been affected by water ingress let’s hope it’s not one of those annoying reoccurring electrical issues that can only be fixed by replacing the parts. As far as where the water is coming in from could be a nightmare to trace. I would ask first is the car normally parked outside exposed to the weather? If so after heavy rainfall have you ever noticed a damp carpet or at the very worst a pool/puddle of water? This clearly would indicate a substantial leak. (Sometimes the leak may only occur whilst the car is in motion & not stationary...) On a couple of Monza’s I have owned they have leaked from the drivers side bottom base of the windscreen however it was never really obvious how it was coming in! One of the car was restored with the windscreen removed & the leak reoccurred a few years later. My solution was to limit driving in heavy rain and wrap both ECU’s in good quality cling film, that solved the electrical gremlins! If you have not noticed a damp carpet then it may be simply a tiny superficial leak which I suspect will be a nightmare to trace. Good luck. |
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Apr 26, 2019 19:25:15 GMT
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The car usually lives outside however it has been garaged while it was misbehaving, two cars but only one garage, there is no damp carpet however he did once have a few drips onto his feet whilst driving, will have to lift the carpet & look for rust marks on the floor.
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