'77 240D Can't start it - PeachParts Mercedes-Benz Forum

adamkat22 · #1 11-23-2011, 09:13 PM

my first car and i'm learning a lot so bear with me. i have a 77 240D that we just swapped engines on. aside from needing a jump start it drove home fine. then wouldn't start again. glowplug strip fuse was blown, so i replaced that expecting it to be solved. no luck. i turn the key and all i get is a painfully slow rolling wheeze. not even a cough or a hiccup. took the gp's out and manually tested them with a battery and they all turned orange. whats my next thing to check? thanks!

toddyvol · #2 11-23-2011, 09:17 PM

How's the battery? A weak or dieing battery will make starting hard.

shadetree77 · #3 11-23-2011, 09:24 PM

yes check the battery and make sure it's the right kind for your vehicle; with the GP's these cars need a big battery with a lot of amps

adamkat22 · #4 11-23-2011, 09:32 PM

put a new battery in the other day. ends up my altnernator had not been working, so i did do some driving on the new one without the alternator though. tried jumping it though with no luck. had the other car revved at about 2000rpm while i tried to start it. maybe i'll get a trickle charger just to make sure. guess these things take a ton of juice huh.

vstech · #5 11-23-2011, 09:49 PM

yup. the glows take a chunk, then while the voltage is down, the HUGE starter cranks on that 22:1 compression ratio... not for the weak minded batteries. best to get a good 850CCA battery in there, most use the group 49 or the MB style 98 I think...
attempting to jump start one of these with a weak battery and your jump car cranking out 2K RPM is a recipe to cook the jump alternator...

kerry · #6 11-23-2011, 09:51 PM

Check to make sure the squiggly wires between the plugs are getting really hot in the glow position. If not, something's funky with the glow plug system. It's easy to get the insulators and wires in the wrong positions on the loop plug system.

adamkat22 · #7 11-23-2011, 10:16 PM

hmm. what would the 'wrong positions' be for the insulators and the wires?

this was a pretty DIY engine swap and some of those copper squiggly wires were bent to fit it seems. one insulator is gone and there is just a nut on there to hold the wire in place.

i should actually see that solid copper get orange when in the glow position?

p.s. i'm charging my battery in case thats the problem, but interested to know about this as wel.

vstech · #8 11-23-2011, 10:20 PM

wait... you have loop plugs, and you tested them out of the engine on a battery?
you have likely damaged the loops... they are only supposed to see 3 volts.

I'd go pick up a set of pencil plugs and rewire your setup if I were you.

but if that's not an option, go pick up a new glow plug, they come with both insulators, and instructions how to install them. then repeat that on all the plugs, making sure the last one from the firewall (the plug closest to the radiator) has the braided cable grounding out the circuit.

vstech · #9 11-23-2011, 10:29 PM

pencil plug heating...

vstech · #10 11-23-2011, 10:31 PM

Loop insulator placement

kerry · #11 11-23-2011, 10:31 PM

Quote:

Originally Posted by adamkat22

hmm. what would the 'wrong positions' be for the insulators and the wires?
.

Current comes in on one wire down thru the loop and back up and out the other wire. The incoming and outgoing wires cannot touch each other. The squiggly wires are visibly orange at night.

Skippy · #12 11-23-2011, 10:40 PM

If the battery is charged and the starter and wiring are all working right the engine should crank over strongly whether the glow plugs are working or not. It actually starting is another matter.

If it turns out you fried your loop plugs, the pencil kind are a good upgrade. I had a car with loop and a car with pencil side by side for several years. The one with loop plugs was a bear to start much below freezing unless you plugged it in. The one with pencil plugs starts the same at 20 degrees as it does at 80.

barry123400 · #13 11-23-2011, 11:08 PM

You did install the engine to ground strap when you changed engines? I assumed the engine cranked well when in the other car?

t walgamuth · #14 11-24-2011, 06:04 AM

Quote:

Originally Posted by barry123400

You did install the engine to ground strap when you changed engines? I assumed the engine cranked well when in the other car?

This is an excellent thought. Be sure of all your connections from the starter to the battery including the battery ground strap.

If it is a fuel problem you can start the engine by spraying WD40 directly into the intake as a primer. It will run off it until you stop spraying.

adamkat22 · #15 11-24-2011, 08:11 AM

ok. wow. thanks for all the info. this is what i know based on what you told me:

i looked at pictures online, and i do indeed have pencil plugs, but they are wired with that squiggly copper (maybe some form of 'making do'). there are only 3 insulators per four glow plugs, so the wires are definately touching each other. that is bad i assume? or only bad if i had loop plugs?

i still need to rule out battery before jumping ahead to other conclusions, but i don't want to mess anything up, so if that is something that is wrong (its very possible there are lots of loose ends like that in this car) then i want to fix it before getting the car running and driving around.

thanks yall!

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