Mechanics

PLEASE HELP! CAR WON'T CRANK WHEN HOT. WORKS GREAT WHEN COLD????

1993 Mercedes Benz 190e • 162 miles

1993 mercedes 190e will not crank when hot. Replaced starter w/solonoid, and new ground direct from battery to frame done with no results. Battery like new. Cranks and runs great when cold. Can hear relays clicking when attempting to start when hot and all lights are on, but will not even crank until cools 30 minutes to an hour. Any suggestions?
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Mooch81
September 3, 2011.



http://www.2carpros.com/articles/car-cranks-but-wont-start

Get a helper disconnect a sparkplug wire or 2 and ground it to the engine atleast 3/16 away from ground-have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, Do you hear the fuel pump come On when you turn key on? If not check fuel pump fuse and fuel pump relay if okay-check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs,coil's resistances,cap and rotor,distributor pick-up coil, ignition control module, cam and crank sensors and computer Note: If it doesn't apply disregard it and keep testing

Rasmataz
Sep 3, 2011.
Thanks for the response. However, let me revise my question. Engine starter will not engage when motor is hot. If restarted immediately, the starter will engage and run without issue. However, if allowed to sit 15-20 minutes, it will not even crank. It is as though power is not reaching the starter. Seems to be obviously heat related. I have replaced starter/solonoid and established a second ground so far with no different results. Any further suggestions?

Tiny
Mooch81
Sep 3, 2011.
Could be a blown fusible link, the starter, starter relay, clutch switch/park and neutral switch/transmission position switch and ignition switch assuming the battery condition and connections are good. Note: If it doesn't apply disregard.

Rasmataz
Sep 3, 2011.
Thanks again for the response. And yes, I agree. I believe it is either ignition switch or neutral safety switch. Looked up how to replace neutral switch and looks to be a pain since it is located on top of the transmission. Decided to bypass with hotwire straight from battery to starter then starter to toggle switch under the dash. Bypassed all the relays and switches. Now starts like a charm. What is strange though is that when I start with bypass toggle then turn back off. It will start again immediately the next time with the key no problem. Not sure, but I appreciate your help.

Tiny
Mooch81
Sep 3, 2011.