hard starting on B100 - PeachParts Mercedes-Benz Forum

sleepstar · #1 09-06-2012, 04:15 AM

what might be a possible explanation for an 81 300D to start hard on B100? on B20 i need to glow for about 7 seconds then crank and it starts on the first turn. on b100 i need to glow for basically the entire time until the relay closes, and then crank for more than a few seconds before it stumbles and catches. once started it runs very smoothly

the primary filter is clean. should i check the spin on filter? none of the fuel lines are weepy (they're all viton)

NCfriend · #2 09-07-2012, 08:58 AM

What is your source for this biodiesel?
Homemade, coop, or commercial?

IT has been awhile since I studied up on bio, but alot goes into finishing the fuel into a "clean" final product: glycerin and methanol extraction, dewatering/drying ...

Has your fuel supplier verified their biodiesel quality to ASTM specs?

Just throwing out ideas.
You guys are chilling off already on the west coast are you? b100 needs to be thinned with dinodiesel in cooler temps

Jeremy5848 · #3 09-07-2012, 10:54 AM

In the San Francisco Bay area one can (I did) run B100 year-round with no problems. My 1985 300D-T had no starting problems with clean commercial B100. I suspect either an IP timing problem or low compression on one or more cylinders.

Jeremy

capflya · #4 09-07-2012, 11:30 AM

Didn't see in your OP but did you verify all your glow plugs are working? That is where I would start if you're having rough start issues. If the timing was off I would think it wouldn't run well once you got it started but that is just IMO. Check our your glow plugs just to make sure their in good order. I had 2 out on my car and it would start but took longer glow cycle to get it going. Replaced all five and we're back in business. Make sure you ream the holes the glow plugs thread in to if you end up replacing them.

If you've been running bio for awhile the spin on filter might be ok. If you have been running primarily dino diesel and just switched to bio I would advise to change out your spin-on for good measure. They're cheap and don't take too long to replace. I would only do that if Bio is new to your car or it's had a good "stint" on dino diesel and now back to biodiesel.

sleepstar · #5 09-07-2012, 02:05 PM

i've been running B20 between fillups with B100. i dont know when the last time the tank was filled with D2... its probably been a really long time because the PO i believe used B100 exclusively. i think i might just change the spin on filter for good measure because i dont know the last time it was done.

capflya · #6 09-07-2012, 11:45 PM

Sounds like a good place to start.

The GP's are easy to check even while in the car. All you need is a multi-meter to test for ohms. If you don't have one let me know, I have an extra one you can have. I work in San Francisco a few times a month so Oakland isn't too far away.

BoiseBenz · #7 09-10-2012, 07:15 PM

Both our 617A and 603A start fine on B100 at 5 dF, with no block heater. You probably need a valve adjustment if the glow system checks out OK.

On the early relays, like yours, if all five plugs burn out, the light illuminates fine.

You likely recall that B100 has a flash point of about 125 dC (257 dF), while D2 is around 25 dC (75 dF). The B100 is no where near as "burny" as is pump fuel, so you need some solid source of combustion: cranking speed and/or good valves and/or good glows.

MB300Dave · #8 09-18-2012, 04:36 PM

Quote:

Originally Posted by capflya

Sounds like a good place to start.

The GP's are easy to check even while in the car. All you need is a multi-meter to test for ohms. If you don't have one let me know, I have an extra one you can have. I work in San Francisco a few times a month so Oakland isn't too far away.

Anyone have a link for GP testing. In the cooler weather it seems like I have one cyl that takes a few seconds to get going on cold startup.

Thanks,
Dave