heavy judder under acceleration

[dav2304]

Hi i'm new to the forum and E21 ownership, recently i bought an 82 316 and have so far not a single bit of bother. but have recently discovered there is a rusty hole where the passenger side front window drain should be flooding the glove box every time it rains and last night it started juddering alot while accelerating and is a bit lumpy at tick over, can anyone help please, also noticed the fuel filter is all but empty, which i'm thinking isnt right.

any replies greatly appreciated

[e21-Mark]

Fuel pump could be throwing the towel in?

[Reck]

81 316 here and had the exact same issue with mine - it was intermittent though, mostly happened during motorway cruising or when trying to burn awat from lights. The fuel pump uses some sort of rubber diaphragm to create a vaccuum I think, and this can wear out over time. I got a new one on ebay for a tenner - they're a piece of piss to fit; remove the airbox, clamp off the petrol hoses either side, undo the two bolts and pop it off. Reverse for refit.

[dav2304]

Thanks for the quick replies its much appreciated. took it out for a spin tonight and all seems well, looking like what you experienced Reck so for the sake of a tenner or so i'll give the fuel pump a bash

[dav2304]

Hi finally got the new fuel pump delivered and fitted, all seemed well at first but then the juddering started again. has anyone got any ideas what to look at next

Thanks in advance for any thoughts

[Reck]

What carb is on there?

[dav2304]

Im not 100% but fairly sure its an original pierburg carb

[Reck]

Ah thought if it was an aftermarket carb it might not have been jetted properly. Tried dumping some carb cleaner in? Might be crudded up. Alot of people suggest upgrading to a weber for better economy/performance and reliability.

[dav2304]

yeah think carb cleaner is going to be the next step. i've read about people upgrading to webers and bike carbs etc but im not to sure what would be best or where to get them set up.

[Reck]

There are a few options for the M10 owner - I use a Weber 32/34 DMTL which I bought used off an E30 and then rebuilt with a refurb kit. Any competent mechanic should be able to get it running but if you want it tuning you want to take it to a carb specialist. You can still buy them new or they come up on here and ebay now and again.

I'm actually converting to an injection setup in a couple of weeks time and might be tempted to part with my Weber for the right amount! But see if the cheaper option does anything first!

[dav2304]

Thanks for all the info. whats involved in converting to an injection setup? sounds interesting. yeah i'll give the cheap option a bash but may be interested in your weber if things dont improve

[Reck]

Well I went for the easiest option which is dropping in an E30 M10 with all the injection gubbins already on there. Needs a bit of wiring, ECU in the glovebox, a return fuel line and in tank fuel pump. There's some threads on here about it if you use the search function at the top.

[dav2304]

tried the carb cleaner, not sure if its helped as the car died the other night turns out the piton on the new pump i fitted had jammed! re-fitted the old pump and it runs so waiting to see if the original problem returns. contacted the guy i bought the pump from and hes saying this can happen if theres no oil to lubricate, seems logical but is this right as i dont recall seeing any.

[Reck]

Dunno tbh mate - The Haynes manual doesn't mention you needing to lube owt before installation. I didn't when I bought mine off ebay and it's been going well for over a year. If that was necessary before installation there should have been some sort of printed warning in the box I would have thought?

Lumpiness and juddering can only be the ignition/fuel system and it's about as basic as it gets on a 316. Have you replaced the leads/plugs/dizzy cap/rotor? Adjusted valve clearances?

[dav2304]

thanks i'll let him know and see what he says but its no great loss either way.

it seems ok at the minute but the problem seems to be periodic so the carb cleaner may have helped but i got a mechanic to have a look at it he thinks its more than likely a carb problem and it hunts alittle on idle. he suggested getting an overhaul kit for the carb or replacing so if you were to sell your weber how much would you be looking for?

havent changed anything else but the plugs, dizzy cap and rotor all look brand new. wouldn't know how to adjust valve clearances but i've got a haynes manual order