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#1
02-24-2008, 06:34 AM
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M110 D Jet 1975 strange starting problem driving us crazy?
Hi all been working on this w114 1975 M110 D jet and now up to the ignition. Ok so the problem:
When we first try and start (hot or cold) she turns over for about half a min as per normal but doesn't catch then it starts to like bog almost like misfire  so we stop and try again & on second attempt it starts in a split second like nothing wrong? We tried this over and over and always the same, first attempt no go it will turn over normal but not catch and then starts to bog down like misfire and or low battery...we then turn off and immediately try again & turn ignition on again and bang she starts first shot  , it has never started on the first attempt even if we hold the ignition for a bit longer, it only starts to bog down like its misfiring??We Went to a few places and made the following changes as per recommendations but still the same problem: was told starter could be faulty so had it tested and it performs as it should, new battery, new clamps, new earth wire & connection, new spark plugs (wr7dc), still the same. the last guy thinks it could be a leaky cold start valve or may need new positive wire?? Anyway anyone else have a similar problem or have any tips to follow up on? thanks 
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#2
02-24-2008, 10:26 AM
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Could well be the cost start injector. It could also be that your system is flooded.
Try disconnecting the electrical connection to the trigger points and then cranking the car. If it acts like it wants to fire up then your system is flooded.
__________________
With best regards Al
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#3
02-24-2008, 11:26 AM
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Disconnect the fuel line to the cold start valve and instead plug it into a fuel pressure gauge that can accurately read 28-32 psi.
The correct behavior should be hitting 32psi when you turn the ignition key to "1" (driving position) and stay there until long after you turn off the ignition. If it takes a bit to get up to pressure that's one kind of problem. If the pressure drops immediately after shutting down, that's another. If having the injector disconnected and pressure gauge in place solves your problem, then, well, you know what's wrong. -CTH
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#4
02-24-2008, 03:21 PM
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To my knowledge, the fuel pump doesn't run when cranking, only before cranking and when running. Now, before you crank, I assume you turn to "Run" and hear the fuel pump buzz and wait until it stops before actually cranking. Try doing this 2 or 3 times before cranking and see if it fires right up. If it does, then you're leaking fuel pressure out too quickly. Leaky injectors (or a CSV) or a leaky fuel pressure regulator could cause this.
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#5
02-26-2008, 08:55 AM
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update...
Ok thanks to all the info so far, checked the CSV, no leak, and turns off after a few turns on the starter, fuel pres at around 30-31 psi and stays there for a long time after engine is off, fuel pump working well
. Not sure what else to try? just strange that it starts first shot on the second attempt? Anyway will take another look at the starter, the only thing that I did notice was the green wire that comes out of the distributor goes (the manual states its the transistorized ignition transmitter) to one of the ignition coil terminals (negative I think) and not to the ignition/switch box like on my other m110?? will look into this further before I try a new starter motor, thanks again :-)
Last edited by body_infinity; 02-26-2008 at 09:02 AM.
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#6
02-26-2008, 10:05 AM
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What makes you suspect the starter motor if it is cranking? I would check the basics: wiring around the starter, battery, and especially the ground straps.
__________________
___ /<>/>/> 1967 230S automatic Boston, MA
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#7
02-27-2008, 04:52 AM
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Quote:
re the wires, the positive (to starter looks good) I have changed the ground wire to a new hi amp version and bolted it to a clean part of the body, there is also another wire that goes from the negative terminal direct to the engine so am thinking its getting good ground as the wire is not hot? anyway will keep looking into this, thanks for the info so far.
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#8
02-27-2008, 07:47 AM
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Quote:
Another thought, is you ignition wiring supposed to bypass the ballast resistor during cranking to ensure a good spark when the battery is being loaded like the V8's or is it different?
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#9
02-27-2008, 11:28 AM
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40 seconds of cranking? Well that's way too much, any battery would start to lose it after that. Even 10 seconds is quite a long time. If you can crank for 40 seconds, bogging or not, then I don't think the starter is your problem, but it probably will be in the near future at that rate ;-) You're definitely getting spark the whole time?
__________________
___ /<>/>/> 1967 230S automatic Boston, MA
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#10
02-27-2008, 09:31 PM
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I have to agree with Todds, 40 seconds of cranking is a long time and enough times doing that and you will need a new starter! it has to be something other than the starter. AS it starts first time on the second attempt my guess is that you have something wrong with the cold start system and the first set of cranking is priming the system (check the continuity and ohms on your thermo time valve). Also as your distributor green wire goes to a coil you probably have the slightly older points ignition in the car rather than an ignitor box. so check the fuel points as well as the points for running the spark (if you haven't already) as Todds says check you have spark all of the time you are cranking
cheers Barri
__________________
61 Austin mini 67 Lotus 7 74 450sl 76 Cadillac 8.2l (501 ci) some new cars megasquirt conversion  on:djet 74 450sl http://www.mercdjetmegasquirt.britautorepair.com/ cis 76 450sl http://www.merccismegasquirt.britautorepair.com/ the best view is always from the point of no return
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