740 GLE 1986 Petrol - Inconsistant Starting - Aaaarr Topic is solved

[Billy UK Newcastle]

This car is superb. We've had no problems with her until this last two or three weeks. For no reason at all, after a drive she fails to start. Its as if there is no spark - turns over but no way. Then you could come back to it in a couple of hours and it will fire first time.

Have checked plugs etc., and they are mint. Runs like a dream once its going. Cant get a mechanic to diagnose cos it always runs fine when under the 'spotlight'!!

I'm not a volvo expert so not so familiar with the terms around the fuel system - but keen to operate as thats where my suspicions lay:twisted:

Any ideas, tips or diagnosis would be truely welcome cos its a bit like russian rulet when my wife takes her out.

Will have to buy a haynes manual as I cant identify the pump fuses or the fule filter etc., Any websites with pictures?
Best Regards
Billy

[A.Baker]

Stop!!!! save some pounds and your sanity. go to volvo .com and order the factory manuals. There spendy but will save you a trip to the chemist.
You never said if it was EFI or cab. my 87 740T had a problem as yours does. There is a sensor in the water jacket under the intake between #3and 4 it's blue. test it for an open. that sensor tells the ECM what temp the engine is.EFI engins. I also found damaged pins on the ECM under the r/side kick panel. Hope this helps.
A. Baker

[LaRy]

It sounds like a typical Volvo problem. Look at the tach-meter, does it show any rpm when cranking the engine? It should at least show 400 - 500rpm. If not, you have no spark. You have probably a broken ignition control unit or a broken Hall-sensor (placed in the distributer). Check also the cable connection for the Hall sensor at the distributer.
I can tell you that your description is typical for this fault. The car runs perfectly and sudden it is dead when you try to start it again. Later it starts again witout problem and can continue to run perfect for several weeks but it will come back and you don't know when.

[[email protected]]

Thanks for that - unfortunately I've just bought the Haynes manual for

[LaRy]

You said that you are going to check the Hall sensor and Ignition control unit, not shure what to check for.

As I said, if the tach is showing 0 rpm when trying to start the dead engine, it is most probably one of those two components, otherwise not. Normally the tach is showing 400 - 500 rpm also when trying to start, if the ignition is OK.

The fact is that the tach is getting it's reference value straight from the ignition coil, low voltage side. So if it is showing 0 rpm when trying to start, you can definitely not have any ignition.

[[email protected]]

OK, understood, but the problem is - its working tonite!!! so everything is cool. Thats the problem with somit like this, you can only really sus it out when it stops working! I looked for the fuel pump relay, but couldnt find one! The car is a 740 GLE saloon and the engine is a 4 cylinder fuel injected, normally aspirated 230E (sussed that all out tonite).

I see the fuel pump under the car - with I think the filter next to it. I will take that off next and check em out and change the filter. Although thre is something that looks like a canister filter (cylinderacal) on the right hand side of the engine bay piping to the injection system - is this another filter or is it some sort of storage device for the fuel?

I still sort of suspect one of the sensors - the hot start kind of sensor - but in terms of checking them, all I can really do is 'replace' them, cos I cant see how you can actually test them.

Still searching for ideas and guidance - thanks loads for so far!
Billy

[Guest]

That is a fuel pump and filter under the car and also under the hood by the r/front of the wind shield. I just rememberd that i had a car that the ignition coil was going bad and doing the same thing. I know this is a pain in the rump. But when the car quits again. Poor lots of gas on it. Light it and run Just kiding. When it quits pull a spark plug wire off of a plug, push a philips screwdriver in the end, rest it on the engine so the shaft of the screwdriver is about 10mm away from metal,Crank the engine and observe for spark. No spark, Bad ignition, Feel the coil if it is too hot replace it. There is a T shaped silver shapped valve under the intake unplug it when the engine is hot and wont start, That is an idle speed control motor. It opens and closes to adjust air mixture depending on the demand. ie a/c on and off hot and cold starts and other loads to the engine during idle conditions. If it starts then plug it back in. chances are the blue sensor i spoke of earlyer is bad. Now we know it is EFI do NOT start engine wile pumping the accelarator pedel. That is one of the jobs of the motor. Keep us informed on you progress.

A.Baker

[Billy]

Hi,
Been travelling for couple of days, but back on the case now. Before I left I checked everything again and found some spurious 'alarm' wires - which I disconnected. Car running great - so told wife all was well. Went to Scotland, and later got call to say 'wont start'. So, now that I'm back, I'll see if it still wont start and check the spark. Then the sensor and get back to ya, thanks for hangin in there.
Cheers
Billy
ps. is there a fuel solenoid somewhere on this car? I've read other trails that refer to the soldering on it, but I cant find one on this car - perhaps wrong model?

[billy]

AFter coming back from scotland to an angry wife - that bloody car wont start, type of a wife, I got into it ready to do the spark tests etc., and it fired first time!! I went out for an hours drive in it, got back and its still working. The car is possessed!
Still looking for the fuel pump solenoid - to check the solder - but still cant find it!
Billy

[Guest]

check out this site http://www.brickboard.com/FAQ/700-900/