Hi all,

Earlier this week I drove my 1985 240 about 800 miles to the mountains. I've been here a few days without any issues; then, today, as I was coming out of a stop, the car hesitated under acceleration and then ramped back up. as I was climbing up a hill subsequently after, it would lose acceleration, then regain it, then lose it until it died. The car would crank normally, but for much longer than normal, and turn over only to run for a few moments before petering out again. So I cleaned the fuel injector wires with an electronics cleaner and it then ran for a few miles fine until the same problem occurred, again on a steep hill. I got back to where I am staying, replaced the main fuel pump fuse and put a new fuel pump relay in, which seemed to help the car crank and start more normally (though still not as it was prior), and it seems to be able to stay running at the moment, but the idle RMP is fluctuating a lot and getting really low sometimes, to the point that it sounds like it is going to die.

I had both fuel pumps and AMM replaced in Jan 2019, so I don't know that they'd be bad, but I also changed the timing belt and spark plugs about 6 months ago. With the fuel pump fuse and relay replaced, I am sort of wondering what the culprit could be?? could it be the engine wiring harness shorting? I just took the AMM out and cleaned it; waiting for it to dry before replacing.

 

you'd need to measure the pump's current draw and pressure to determine if its electrical in nature... Have you replaced the filter recently? Also wondering if you have an issue with the tank venting. Does it behave different with a full tank vs almost empty?

 

I do not know if the filter was replaced; the job was done by a firestone at that time. I would think replacing the filter would naturally follow replacing the main pump but with Firestone.... I will check the pump's draw but I don't have a pressure gauge.

I have not noticed any difference in behavior with low vs. high fuel levels.

 

so after replacing the fuel pump relay, cleaning the AMM and replacing the main fuel pump fuse, the car seems to be starting and idling normally. I have not driven it any distance yet... but i can hear the main fuel pump operating.

 

i would /never/ bring a european car to a place like Firestone for *anything*. In fact, I wouldn't trust the local Firestone to change the oil on my Ford truck.

 

straight up right!!!??? learned that one the hard way. been doing my own maintenance and work ever since. those fools didn't even solve the problem at that time!!!

 

Does the problem happen when you have less then a half a tank of gas. Also is the fuel pump nosier then it used to be.

 

I discovered, in the course of jumping the fuses to verify both pumps were working, that #4 in-tank fuse was burned. I replaced it and drove up the road a small distance and the car seems to run normally. After, I jumped left #6 to left #4 and could hear both pumps operating. I typically check the in-tank pump by listening in the trunk above the gas tank...

in any case, my suspicion is that the fuel pump relay may or may not have been bad, but the in-tank pump was not working due to the blown fuse that I didn't catch. hence the car's normal operation until there was a steep grade to ascend. my 3/4 full tank also masked the bad in-tank fuse until the grades.

 

The question becomes - why did the fuse blow? Fuses are there to protect wiring when there is too much current draw.

Since your car is in the years of the biodegradable wiring, I would check out the wires that run to the in-tank pump.

 

problem arose again and I think I have it figured. The wires/terminal to the ignition harness off the distributor are lose and causing intermittent failure of spark. looks like this is the part:

https://www.fcpeuro.com/products/vol...245-1237031292

jostling this connector will intermittently lead the car to die.

rest of ignition system checks out, fuel pumps working, AMM cleaned and functional, spark plugs goods....
.

 

here's a quick vid of the problem after installing new engine harness. jostling the terminal off the distributor kills the car.

 

Alright I am back. I am going to adjust the idle speed and ignition timing after this repair - but wth, my '85 240 doesn't have an RPM gauge?? I have no idea why this is the case - strangely, my grandfather had a volt meter and OPS put in the dash... but no rpm.

EDIT: to be clear, I've noticed this before, but only when reading the procedures for ignition timing did I realize how it disadvantages me.

 

tachs were optional. our 87 240 GL had one.

an old fashion dwell meter usually had a tach mode, you clip it to the battery and to the "1" signal on the side of the ignition coil, set the number of cylinders. alternately, you should be able to use a digital multimeter that has a 'Hz' frequency setting, clip it to the #1 terminal on the side of the coil and to ground, then take the reading in Hz, and multiply by 30 to get RPM (so 25 Hz would be 750 rpm) on a 4 cylinder (30 == 60 seconds/hour / 2... use 20 = 60 / 3 for a 6 cyl, and 15 for a V8).

 

thank you for the info pierce!

i got the new hall sender today and have a couple questions about its installation.

here's the old hall sender and its position in the distributor:

old hall sender position

this is the new hall sender, which positions differently in the distributor. is this the correct installation?

new hall sender, resting on unit, not installed

I presume this spacer, underneath the old hall sender, must be removed, since the new unit has a spacer under it already?


spacer underneath that needs removal?

does this all look about right or no?

 

i never had to replace the hall sensor on our 240, and my 7/9's were all LH 2.4 so had a CPS instead. last distributor I had apart was on a 1966 VW and used breaker points

 

that ended up being the wrong part for my distributor. learn from my mistake: double-check fitment notes!

 

new hall sender is in. car is running normally and all parts of the ignition system check out EXCEPT one small thing I can't figure.

When testing the ICU switching function, the hall sender terminal is disconnected and terminal B jumpers to C. each time it's jumped, a spark should fire at the plugs. this simulates the hall effect sender timing to the ICU and back over to the spark plugs through the coil - if I understand that correctly. despite the car starting and running fine with the new hall sender, when performing this test, I only get spark through wire #3; wires #1, 2, and 4 do not produce a spark at the plugs during this test.

with everything buttoned up correctly and cranking the engine, there is spark at each plug wire.

so does this indicate a small fault in the ignition harness or the plug wires perhaps? or is it just a fluke that I should ignore?

 

if the engine isn't turning, the distributor isn't either, and the rotor in the distributor will only be pointing to one of the plug wires, apparently #3...

 

wow, hadn't thought of that. thanks pierce, i appreciate you.