My buddy and I've been working on my '85 240 DL and installed a new water pump, timing belt and radiator in that order. However, the car is currently only cranking and not starting; we believe it's an issue with our timing.

First, we did not align the crankshaft pulley to TDC before removing the 24mm bolt. I don't think that would make a difference in terms of installing the new belt.

We installed the new belt and aligned it to the crankshaft first, then to the cam and intermediate. We did this because, when we aligned the belt to the cam and then the intermediate, the double mark on the timing belt for the crankshaft was one or two teeth off of the keyhole and alignment mark on the crank sprocket; there was also significant play in the belt between the cam and intermediate shafts.

We installed the belt and upon manually cranking the engine, the gears were timed correctly. We then reinstalled the crank pulley, covers and drive belts and fan

We also do not have the special tool to hold the pulley in place while removing/installing the pulley. We manually torqued and loosened the bolt.

So what are we missing? Thanks for any advice.

 

I think you need to go back and re-time it. Here is a link that has a good description of how to align the timing marks:

https://www.brickboard.com/FAQ/700-9...Series_Engines

Line the cam sprocket to the mark on the timing belt cover. Same for the half-shaft sprocket. Then line the crankshaft key to the mark on the engine block. With them all lined up, install the timing belt over the pulleys.

From your description it sounds like you are using the marks on the belt to align your timing. I have heard that they can be wrong but I've never experienced it. If you line up the pulleys as described in the link it really shouldn't matter.

By the way, are you replacing the belt due to preventative maintenance or did the old one break?

 

How did you "loosen" the crankshaft bolt? Sometimes the centering nub gets sheared off and the timing won't hold... Other than that, I would not use the timing belt marks either.

 

We trapped the flywheel. And it is for preventative maintenance. The old belt was worn too.

We re did the belt and the car is running. However, the ignition timing appears to be varying from 10-15 degrees. Now the Bentley manual lists the spec at 12 + or - 2 degrees, but I assume the timing should be consistent? The idle is a bit rough too, which I assume is a function of the ignition timing varying

Additionally, we have the distributor in a rather extreme clockwise position to have the ignition timing as it is currently

If this is a problem, does it suggest improper timing belt tension/seating? When I installed the belt today, the sprockets and belt marks we all aligned perfectly, but there did seem to be slight excess slack from the cam to intermediate shafts. But I don't know how that could be remedied, as the belt is the correct size.

 

We redid the timing belt and the car is running well - better than before. However, the ignition timing is still varying; it is jumping from 13-9 degrees off the flywheel markings on the lower timing belt cover. And the car still gets small, rough splutters consistently in the idling. That is a problem I've had for at least a couple months that seems to be better now but still present.

Any thoughts on what this might be?

 

I'm not so familiar with the '85 but I believe it has a hall sensor on the distributor that delivers the timing pulses. I know on an old chevy V8 I had with a hall sensor ignition that worn bearings in the distributor caused jittery timing. Maybe others with more experience with this model year could chime in.

 

indeed, a 85 has a hall sensor in the distributor, advance however, is managed by the ICU and a vacuum line to a 'bellows' at the bottom of the ICU

 

take a small tack hammer and tap each injector. If one of them is stuck, it will cause this. I got mine running by tapping on them to free them up. Free hack.

 

in a former life you probably were named 'the fonz'

 

I'll try tapping on the fuel injectors.

I also bought some GumOut PEA cleaner. I just filled up the other day so I'm waiting until it gets low to use it. Has anyone had good experience with this stuff?

 

if it is similar to SeaFoam, then yes it works well.

 

I've never had any luck with seafoam or any other injector cleaner. had a CIS (KE-Jet) mercedes with shot injectors that stumbled and stalled at idle... no amount of seafoam made things better. new injectors made it run like a new car.

 

Pierce, you've mentioned in other threads about the wiring harnesses on these cars going bad - I assume that could be causing this issue too? As in, the engine harness that attaches to the fuel injectors (I assume that's what those wires are?) could be intermittently bad or have a small short, causing small tremors in the idle?

In which case, how hard are replacing these harnesses? I saw that the engine and ignition harnesses are ~$600. But does it require taking the engine apart?

 

I've never changed a harness on a 240 or 740, but what I would do is lay out the new harness parallel to the old one, make sure I know where every connector is going, then unplug the old and plug in the new one section at a time. the injection harness goes through the firewall to the ECU and fuel system relay, so I'd probably start at that end.

IIRC, the years for bad 240 harnesses are about 1983 to mid 1987. our late 1987 had a good harness. the bad ones will have the insulation cracking and flaking off inside the black outer sheathes.

FWIW, my 740T had the same little intermittent stumble the whole time I had it, nothing I did affected it, it was a 1992, long after the bad wiring era. My suspicion was always that it was ignition, but it was never bad enough to matter.