Mk3 Cavalier Owners Club | Vauxhall Cavalier Dot Com

Hi there, need help with Cavalier engine running rough, changed all electrical items as follows:, spark plugs, ht leads and coil, crank shaft sensor, fitted refurbished fuel injectors, and pruven working Ecu. Belled out conn sections from crank sensor to ecu, checked compression, is 162 to165psi no change at all.

I would check the wires to the injectors.

It is not unusual for the wires at the injector connectors to deteriorate.
I have heard of injector wiring failing due to the hot environment of being sat on top of the engine on a 30-ish year old car.

Plus, I assume the plastic injection loom trunking is fully seated on the injectors.
I have no clips on mine, so from time to time I have nudged the trunking off the injectors causing a mis-fire.
Thankfully it remains seated once I have reseated it again.

Thanks for your reply, all injectors klicking, the long screwdriver test to ear, forgot to mention that I changed the cam belt, both timing marks line up spot on the crank pulley to rear cover and the cam pulley to the top marks, after running the engine for few minutes, noticed black fluid running out from fist exhaust joint, the one with springs, I think it can be unburnt fuel or coolant? Lot of black smoke at the back of the car when reving up the engine. On tick over the engin hunts from nearly stalling to to 700rpm up and down, I am trying to avoid removing the head, also checked the ht with I line spark checker, all 4 are working as they should. Is there anithing else I can check? Not checked with a timing light yet, don't have one, do I need to get one?

Hunting sounds like an air unduction leak, where the ECU is struggling to control the fuel / air mix.

Does the engine management light come on?

If the engine light does not come on whilst the engine is running,
Consider the likelihood of an air leak.

You have already tested the injectors, and I am assuming you have checked, cleaned or replaced the rotor arm and distributor cap too.

Inspected and cleaned the the rotor arm and the distributor before I decide to change the ht leads and coil, as I mentioned I fitted Accuspark testers in line and they are all lighting up in correct firing order, removed the plugs and found 1&2 with black coating but 3&4 very clean but slightly oily, so I assume that 3&4are not doing much to the internal combustion. Regards air leak, I have replaced most of the breather hoses, and the air filter.
The engine light goes out after the engine starts, every time. Did the paper clip test as per your instruction, and got alarm 31,so I changed the crank sensor but no change. I keep thinking it is a timing issue because I fitted new cam belt, would the engine start if it is one tooth out of position back or forward?

The engine will indeed start if it is out by up to a couple of teeth.
But it will run quite rough.

Thanks for that, it is running very rough now so it may be the cause? I have the engine auxiliary belt and crank pulley off but the cam belt in place, I know I may be asking too much, but could you run me all the checks and settings I can do from this point on. Thanks

Assuming you have the 1993 onwards engine with the timing belt tensioner roller...

This is how I did my C18NZ, but all the 1.8 and 2.0 8 valve engines are done in the identical way.

viewtopic.php?f=70&t=4047

I converted to C20NE in 2012, and can confirm the set-up is the same.

Thanks Robsey, great help with upside down U on the crank pulley and above the sump cover, all lines up perfectly, so I can eliminate the cam belt. I m happy with the ht side as there is good spark on all 4 plugs I think it only leaves the injectors. Could there be a wrong fuel pressure and how can I measure it, I could try to rig up some think to measure the output from each inti a bottle, but would be difficult, what do you think?

The injectors all use a "common" fuel feed rail, so if fuel pressure was an issue, it would cause all injectors to struggle.

In my experience, the car would idle quite merrily, but would splutter and struggle if you rev it or try to drive it under load.
The only way to rev with poor fuel pressure is to slowly press the accelerator to allow the revs to build up gently.
This is based on having the wrong fuel pump fitted, and the pump being unable to supply at a high enough line pressure.

You appear to have a good spark,
You have no Engine management light on,
You have a mis-fire, rather than classic fuel starvation issues.
So....

This narrows it down to the injectors themselves.
After nearly thirty years, it may be that they need a good clean and service.

They may have a bit of gum or grit causing congestion, which is adversely affecting the spray pattern of the injectors... two sound like they are worse than the others.

The best method is to send them to a professional injector cleaner.
Otherwise, you could try adding an injector cleaner to your fuel, or spraying a cleaner spray into your air intake (air filter).

Be aware though that the sprays will often cause the engine to surge, so only spray in brief pulses.

Hi Robsey, I think that I have created my own problems, replaced both fuel lines two months ago, I may have reconnected the hoses wrong way round, the one from the pump via the fuel filter I have put it on the pend of the fuel rail in the book it says should go to the fuel regulator
Just swapped them but the engine refuses to start.
Does the disc shape, which I think is a non return valve, be in the feed or return line?

Maybe you have two plug leads wrong if you replaced them, or diff distributer cap?

Hi everyone, if you have cavalier mk3 sri 8valve can you check were does the feed and return fuel pipes connect to on to the fuel rail, I think the feed pipi is from the fuel filter.
Thank you

If I remember I will try and check my diplomat's fuel connections at the weekend. Can I ask how this issue started, you mentioned replacement of fuel lines 2 months ago. Was that just general maintenance or due to fuel lines burst or something else? Did the fault happen suddenly or progressively?

Have you tried spraying brake cleaner round the induction area, round injectors etc? Be careful with fire risk obviously don't spray on exhaust manifold or when the engine is hot, use wd40 if you're worried about using brake cleaner.

I am in the process of saving the car from being scrapped, I am near completion of fully restoring the car so renewing the fuel lines was part of it, I think that I have found the problem. The fuel pressure regulator appears to be faulty, after watching on you tube how to test it, but I am finding it very hard to find a replacement, don't want to pay £175 for one from Germany, any suggestions?

I think the Bosch number for this part is 0 280 160 221, and the GM No: 90166629

Number 1 part here: https://opel.7zap.com/en/car/j89/g/0/87-1/#2

If you do a google search for the bosch part number (bosch "0 280 160 221") or (Opel "90166629") you get a good selection, you might find a new or 2nd hand parts here. Yes, parts for the cavys are becoming very rare now, stock up while you can!

Thank you guys, the cavalier is running great now, fuel pressure regulator arrived this morning from China brand new, it only took 7 days from order. The price was not £175 nor £190 as quoted on ebay but with delivery charge was £13.49, identical to the original and resolved the rough running. Took over two months to get to this point, after changing all electrical items, plugs, plug leads, ht coil, crank sensor and even the ecu, and second hand working injectors, spent a small fortune on compression test kit and fuel pressure kit, only needed to change the fuel pressure regulator. Well it won't heart to have replaced 30 years old parts, next job after wheels powder coating and new tyres will be to get an Mot.