unpredictably started right up - PeachParts Mercedes-Benz Forum

pselaphid · #1 09-20-2007, 07:04 PM

I drive the 300d (225K) almost daily, diesel around town, hot WVO on highway. It always starts and goes within a second or two of cranking. It ran fine yesterday and this morning wouldn't start...acted like a no fuel/glow plug failure...just wouldn't fire at all. Glow plug light came on, normal cranking speed, no reason to suspect plugged filter or priming issue based on previous behavior or tinkering. Cranked it till the battery ran low then hooked a charger to it. Took truck to work and worried all day. Returned with a head full of things to check, starting with the usual suspects; glow plugs, filters, and mentally working my way through the IP towards a new engine. Turned key and it fired right up, hiccuped a couple times, then ran as normal. Shutoff and subsequent restart normal.

Opinions welcome about why it started one day, wouldn't fire at all the next morning, then fired right up that afternoon without intervention. I don't mind repairing problems, but I hate it when things work/don't work on an unpredictable schedule...makes for nervous trips to the airport. I realize lots of threads deal with hard or no starts, but I'm looking for clues to a transient no start situation. Things just don't fix themselves and I suspect its symptomatic of some problem that's likely to get worse.

I just restarted it and noticed that the glow plug light came on for a few seconds AFTER the engine started. That seems to be a new feature. Glow plugs and relay are only a year or so old. Does this indicate a bad G.P. circuit? Fuse is intact.

kerry · #2 09-20-2007, 07:07 PM

Hairline crack in the strip fuse? Air in the fuel lines, purged out just when your battery went dead. Bad condensor or points.

pselaphid · #3 09-20-2007, 07:13 PM

I'm leaning towards a glow plug issue. Points, condenser? I can't even find the distributor.

bellyboy · #4 09-20-2007, 09:12 PM

it sounds as if it is cranking.

i would suspect (hopefully) some bad fuel. disconnect fuel line get a cup of clean diesel dip line in it let it run for a bit. if it is bad drain or cut with kerosene-change filters

i dont think this is it but it is easy to rule out. air in the lines -crank with fuel cap removed a rag in its place- wouldnt crank to long maybe 10 seconds max- if it doesnt work after this you are clear of air

easy on that starter dont over heat it

biobenz240d · #5 09-20-2007, 10:18 PM

I'd check the glow plug relay connections for corrosion or loose fit .

pselaphid · #6 09-20-2007, 10:31 PM

Thanks, I haven't been able to reproduce the problem, but I'll retry on a cold start tomorrow. GP relay and GPs are only about a year old, but I have an old relay that would be a good switchout if it does it again. Based on the fact that it runs smoothly once started, I'm tending to rule out a fuel quality/delivery problem. Finger pointed at glow plug system for now. Anyway, if I can put my finger on it and its interesting and/or hasn't been covered ad naseum before, I will pass it on.

lietuviai · #7 09-20-2007, 10:51 PM

You say you run WVO? I'm assuming you have a two tank system since you had hot WVO. You probably have some sort of tank selector valve and that is probably the problem. It might have been stuck not allowing fuel from either tank to get to your IP.

pselaphid · #8 09-20-2007, 11:09 PM

Yep, dual greasecar three ways. That would be a new and different problem, but I think I would have gotten a startup before fuel starvation set in. Hadn't switched valves in a couple days prior and was running fine on the previous shutoff. But, an astute observation, thanks.

benzforlife · #9 09-20-2007, 11:16 PM

not sure what ur climate is but, if u have cool nights and mornings and u still had a bit of wvo in there, that may have plugged things up a bit.
When it warmed up it could have liquefied it better?

pselaphid · #10 09-20-2007, 11:28 PM

South Louisana, warm to hot. Pure diesel in the system at the time of the incident. I'm always vigilant about that veggie stuff, though I did initially wonder if all the dire warnings were true. Very happy when it started and ran again. Keep em comin'.

Da Hawaiian · #11 09-21-2007, 10:17 AM

SAME thing happened to me this week, running SUPER, then died out and chugged and then wouldnt start. Sat for 2 days while I freaked out..

Went out 3rd day tried to start..chug chug chug Eueka..she started....no visable or noticable leaks or fluids..tightend the primer pump down and viola~Drove 25 miles back and forth to get new Vet plates for the car..NO problems..Lucky us...

Dakota

W123 300D 1981 "helga" 194K

pdxwaker · #12 09-21-2007, 10:55 AM

My guess is air in the fuel lines that was eventually purged by cranking... not sure what your fuel return setup looks like in the WVO system...

vstech · #13 09-21-2007, 11:27 AM

are you using pollac valves? greasecar uses the plastic valves and they tend to suck. look to frybird (and plan on waiting a while for shipment...) MUCH better valves!

pselaphid · #14 09-21-2007, 12:36 PM

Nope, no pollacks, the ones I have (see note below) seem to be good quality. I've never experienced any obvious problems in the three years I've had them, not to say I won't. Fuel return is a loop on WVO, but, I repeat, no WVO is involved in this problem. I can tell because I have clear prefilters that will allow me to identify which fuel is going where, especially before entering the IP, and also spot bubbles. Neither seemed to play a role. I am going to switch out the gp relay later today and see if the odd symptoms go away or at least change (in case the older used unit also has problems), then I'll start testing the GPs individually. I'll be relieved if its GPs, but not happy about having to fix them after a major upgrade less than a year ago.

As an aside, the valves I have are as seen here:
http://www.greasecar.com/product_list.cfm?cat=Individual%20Components

Are these giving people problems? I would consider an upgrade to frybrid if there is a good reason to do so.