starting problems with monza

[muscle_car_man]

hey

i am having problems statring my 86 monza!it takes 2-3 times turning over b4 she willl start.then when it does it misses for about 3-5 secs so im guessing the fuel is getting through.i have only just replaced the thermostat asswell,can any1 help me

cheers michael

[GTJIM]

The Opel injection set-up rarely needs any adjustment and starting problems are usually confined to the ignition/electrical system.
Make sure you have NEW spark plugs and the dissy cap/rotor is OK.
Other than that sometimes the injectors need cleaning if there has been water in the fuel at any time as this rusts them. Also check that the fuel pressure is in specs (35 to 42 psi). The fuel pump only starts to pump up to pressure once the airflow valve is moved by the air being sucked into the motor so it always takes a turn or two of the motor before fuel pressure is available at the injectors with the Bosch FI System.
Opels have a nasty habit of reducing the voltage of the electrical circuits while starting too - due to the overloading of the ignition switch. See "Otto Start" ... the Monza uses the same system as the GT for a switch so still has the same problems!
Often, hard starting is a combination of ALL these things.

HTH

[muscle_car_man]

hey

yea i only just recently replaced the spark pugs and cleaned the airflow meter out!!!do you think i should try a new set of leads and coil??

cheers michael

[ard674t]

How long have you had the problem?

I've had that problem for pretty much as long as I've owned my Monza (9 years and 110,000 miles).

I'd tracked the problem down to fuelling, and even made up a little resistor and relay combination to fool the injection system into giving the car more fuel when it started up. What I did was to wire up a relay to put a fixed 2k2 resistor onto the injection's temperature sensor wire when starting, flipping back to the temperature sensor itself once you let go of the key. Worked like a charm, but it bugged me that I needed to do that as it clearly wasn't needed when the car left the factory.

You can simulate this behaviour by holding the temperature sensor plug off the sensor while someone cranks the engine and plugging it back on the instant the car catches (which will be almost immediately if you have the same problem as me).

Over the years I've changed pretty much every component in the injection and ignition systems but nothing changed the way it worked. Until last weekend, that was. The car was clearly getting to the point where I needed to get the injectors cleaned so I whipped them off and sent them off for cleaning. Unfortunately I needed to use the car and that meant I had to break out the 6 brand new injectors I had in stock and put them in.

You guessed it, that made the difference. The car now starts really quickly in the mornings.

The way I've rationalised this is that, even though I had cleaned the injectors a few times in the past, the maximum flow rate of the injectors wasn't up to factory spec, even though they worked well at lower flows. Since you need so much fuel while cranking, you're really dependent on the maximum flow rate, and since it wasn't up to spec, the car didn't get the fuel it needed to catch. Taking off the temperature sensor plug while cranking made the ECU think it was 40 below, so it poured as much fuel in as it could, and that was enough to start it.

That also explains why this phenomenon is car-dependent. My other Monza starts almost instantaneously, but the one we use every day is the one that used to take the cranking. Of course, the other Monza doesn't have anywhere near as much mileage on the injectors.

HTH.
Cheers,
Nick

[Stipe77]

You've mentioned "cleaning injectors"? That's interesting, I've never heared about it. How do they do it? Is there any way to do it at home? I am asking because my injectors got stack probably because of riding on LPG (Liquid Petroleum Gas).

[GTJIM]

Originally Posted by Stipe77 You've mentioned "cleaning injectors"? How do they do it?

Injectors need to be removed from the manifold to be cleaned properly by ultrasonic cleaning. Not a Do-it-yourself job!

If there is no specialty fuel injection repair shop near you then a visit to a diesel truck repair shop should be able to help you.

With LPG the injectors just sit there and gum up - plus the rubber fuel lines deteriorate. A good shop not only cleans the injectors of fuel varnish and carbon build-up but also replaces the fuel hoses and checks the flow rate of them too.

Monza fuel hose tails are well known for leaking fuel all over the exhaust manifold creating a very dangerous situation!

Here is a rundown on Bosch injector ceaning from a Jaguar website:
http://www.jaguarfuelinjectorservice...0injectors.htm

[Stipe77]

Thanks GTJIM. I've goggled some places I can do it near me but the price surprized me. I would have to work for 12 hours to get one injector renevd. I've tried some of thees fuel additives but it didn't work. One guy advised me some special injector cleaner that you pour into as little amount of fuel as you can. I obtained two bottles of it and pour it in. As a result engine stopped and doesn't go on fuel anymore. Fortunately it steel rides good on LPG.