316 M10B18 Carbed fuel issues?

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MyNameIsOllie
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Wed Apr 25, 2018 5:35 pm

Hi there,

Fairly new to the E30 game as this is only my second car (first being a Mk2 Golf Ryder, so not completely new to the carburetor world) and I recently bought a poverty spec 316.

The car has been great, but recently has started juddering at low speeds and even went as far as to shut off when I stopped to give way to a car at a junction - I put this down to low fuel pressure, as the fuel filter is empty and it seemed like the logical conclusion. A few weeks ago, this juddering happened at motorway speeds - the car refused to go above 50 mph. Obviously this is really dangerous!

My question is: what is causing this? I figured it was the fuel pump, although I have been confused by the many different fuel pump configurations on the various trims of this car. Being a carbed model, I am aware it has a pump on the side of the cylinder head - am I correct in assuming there is also an in tank pump?

Any help will be greatly appreciated!
Ollie
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Wed Apr 25, 2018 8:37 pm

Hello Ollie. Does your car still have a Pierburg carb or is it a Weber?
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MyNameIsOllie
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Wed Apr 25, 2018 10:13 pm

DHFiS wrote:Hello Ollie. Does your car still have a Pierburg carb or is it a Weber?
Yeah, the car is completely standard
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30316
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Thu Apr 26, 2018 3:15 pm

MyNameIsOllie wrote:
DHFiS wrote:Hello Ollie. Does your car still have a Pierburg carb or is it a Weber?
Yeah, the car is completely standard
From the description it sounds like the dreaded Pierburg carb issue. Best bet is to replace it with a Weber carb. In the past I have managed to repair a Pierburg by replacing spring loaded plunger on top of the carb as it wears and lets air through. It’s a machine shop job as it is a press fit. 10 years ago the part was available from dealers but I am not sure if it’s still the case.
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martauto
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Thu Apr 26, 2018 4:31 pm

Put a weber on and you will notice the difference.

Mart.
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MyNameIsOllie
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Thu Apr 26, 2018 5:48 pm

Thanks for the help guys, will definitely look into getting a Weber. Is there anything else it could be? Should I also replace the fuel pump(s)?
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Thu Apr 26, 2018 9:39 pm

MyNameIsOllie wrote:Thanks for the help guys, will definitely look into getting a Weber. Is there anything else it could be? Should I also replace the fuel pump(s)?
It’s unlikely to be a fuel pump problem, though do check that no air is being sucked in around rubber pipe joins. Look in the inline fuel filter to make sure it’s not running out. It’s easy to see since it is transparent.

One possibility is to check the rubber insulating thick gasket under the carb has not become porous. It gives similar symptoms.
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MyNameIsOllie
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Thu Apr 26, 2018 10:33 pm

30316 wrote:
MyNameIsOllie wrote:Thanks for the help guys, will definitely look into getting a Weber. Is there anything else it could be? Should I also replace the fuel pump(s)?
It’s unlikely to be a fuel pump problem, though do check that no air is being sucked in around rubber pipe joins. Look in the inline fuel filter to make sure it’s not running out. It’s easy to see since it is transparent.

One possibility is to check the rubber insulating thick gasket under the carb has not become porous. It gives similar symptoms.
The fuel filter is consistently empty/almost empty, which is what makes me think that it's a fuel pressure issue. I'll check the gasket before buying a new carb, good shout.
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Fri Apr 27, 2018 8:44 pm

Fuel pump failures are rare but not unheard of. Pierburg carb failures are very common.
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Brianmoooore
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Fri Apr 27, 2018 10:17 pm

Take the fuel hose off of the carb. and crank the engine. Fuel should flow from the pipe at low pressure (0.1 to 0.3 bar, according to Autodata). Let it flow into a container, and hold the end so that it is immersed in petrol. Shouldn't be air bubbles.
If a fuel filter is mounted horizontally, then it'll always be nearly half full of air. It needs to be held vertically, with the outlet at the top to expel all the air.
I'd go a bit further than DHFiS, in that I'd expect that an E30 original carb. in full working order to be almost unique.
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MyNameIsOllie
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Sat Apr 28, 2018 1:09 pm

DHFiS wrote:Fuel pump failures are rare but not unheard of. Pierburg carb failures are very common.
Okay thanks, I'll get to work and report back once I find out more.
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MyNameIsOllie
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Sat Apr 28, 2018 1:11 pm

Brianmoooore wrote:Take the fuel hose off of the carb. and crank the engine. Fuel should flow from the pipe at low pressure (0.1 to 0.3 bar, according to Autodata). Let it flow into a container, and hold the end so that it is immersed in petrol. Shouldn't be air bubbles.
If a fuel filter is mounted horizontally, then it'll always be nearly half full of air. It needs to be held vertically, with the outlet at the top to expel all the air.
I'd go a bit further than DHFiS, in that I'd expect that an E30 original carb. in full working order to be almost unique.
Great idea, will try this asap and get back to you!
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MyNameIsOllie
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Sat Apr 28, 2018 6:59 pm

Okay, so I had a look and experimented with the carb's fuel lines and found that when disconnected, no fuel was flowing. However, when reconnected there was a slow trickle of fuel entering the fuel filter, so that makes me think that the pump is on its way out.

Another thought occurred to me; is it possible that the timing is ever so slightly off?

I think I'll replace the pumps first and if the problem persists I'll re-time the engine. If it still judders, then I'll buy the Weber (I'll probably get one anyway just because).
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Brianmoooore
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Sat Apr 28, 2018 9:21 pm

If there's little or no fuel coming from the disconnected fuel line when you crank the engine, then this is the reason for your problems.
Are you sure that there is fuel in the tank? The only two times in my life that I have been driving a car that would go no further, this has turned out to be the cause, in spite of gauges indicating otherwise.
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MyNameIsOllie
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Sat Apr 28, 2018 9:27 pm

Brianmoooore wrote:If there's little or no fuel coming from the disconnected fuel line when you crank the engine, then this is the reason for your problems.
Are you sure that there is fuel in the tank? The only two times in my life that I have been driving a car that would go no further, this has turned out to be the cause, in spite of gauges indicating otherwise.
I filled the car up maybe two weeks ago and haven't driven it since. Do you have any recommendations as to which fuel pump to get?
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MyNameIsOllie
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Mon Apr 30, 2018 8:46 pm

I made a short video to better describe the problem:
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Brianmoooore
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Mon Apr 30, 2018 9:02 pm

You have a 'choke' knob. No E30 had one of these, so you are mistaken that your car is unmodified.
Need to know what is fitted before going further.
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MyNameIsOllie
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Mon Apr 30, 2018 9:33 pm

Brianmoooore wrote:You have a 'choke' knob. No E30 had one of these, so you are mistaken that your car is unmodified.
Need to know what is fitted before going further.
Yeah I should've mentioned that beforehand, the seller said that he fitted a choke to the stock carb. Whether this is the truth or not is unknown.
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martauto
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Tue May 01, 2018 5:10 pm

MyNameIsOllie wrote:
Brianmoooore wrote:You have a 'choke' knob. No E30 had one of these, so you are mistaken that your car is unmodified.
Need to know what is fitted before going further.
Yeah I should've mentioned that beforehand, the seller said that he fitted a choke to the stock carb. Whether this is the truth or not is unknown.
The stock carb was a work of art and was an automatic choke which did not have a choke lever.
This said, it broke down quite early in its life and caused sooooo many problems people put a weber on and it cured it all and also had a "choke" lever.
Brian is right, have a good look and see what is actually there.


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MyNameIsOllie
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Wed May 02, 2018 3:54 pm

Okay, will do. My bad!
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MyNameIsOllie
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Sun May 06, 2018 12:12 pm

Alright, so after stripping things back a bit, it has been revealed that the car does, in fact, have a Weber :? What should I do now? Is it possible that it's the gasket where it joins the intake manifold? Could it just be dirty?
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Brianmoooore
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Sun May 06, 2018 4:22 pm

Brianmoooore wrote:If there's little or no fuel coming from the disconnected fuel line when you crank the engine, then this is the reason for your problems.
There's very little likely to go wrong with a Weber, as long as it was jetted correctly in the first place, and gets clean fuel.
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MyNameIsOllie
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Sun May 06, 2018 5:12 pm

Brianmoooore wrote:
Brianmoooore wrote:If there's little or no fuel coming from the disconnected fuel line when you crank the engine, then this is the reason for your problems.
There's very little likely to go wrong with a Weber, as long as it was jetted correctly in the first place, and gets clean fuel.
Hmm, do you think it could be the fuel pump or the timing then? Might be one of those things I take the car to a dreaded garage for a diagnosis...
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Sun May 06, 2018 9:35 pm

Timing will not affect the amount of fuel that comes through the fuel pipe on a basic carb car.

Either the fuel pipe is blocked/leaking or the fuel pump is not working.

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MyNameIsOllie
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Mon May 07, 2018 12:29 am

BenHar wrote:Timing will not affect the amount of fuel that comes through the fuel pipe on a basic carb car.

Either the fuel pipe is blocked/leaking or the fuel pump is not working.

Ben
Alright, I'll replace the pump then. Worth changing the pump relay too? How would I know if the pipe is blocked?
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30316
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Mon May 07, 2018 7:45 am

MyNameIsOllie wrote:
BenHar wrote:Timing will not affect the amount of fuel that comes through the fuel pipe on a basic carb car.

Either the fuel pipe is blocked/leaking or the fuel pump is not working.

Ben
Alright, I'll replace the pump then. Worth changing the pump relay too? How would I know if the pipe is blocked?
Pump is all mechanical. No relay for pump.
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Mon May 07, 2018 11:15 am

No electric pump on these, so (shouldn't) be a pump relay to change.
Lift up the rear seat base, remove the oval inspection panel, and remove the tank level sender and pick.
You will now have the pipe that leads to the pump disconnected, so it will be easy to check if it is blocked or leaking, and be able to see if there is anything wrong with the pick up pipe.

P.S. Just typed all the above while still on page 1, without noticing that a second page had started, so apologies to 30316 for duplicating some of his post!
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Mon May 07, 2018 12:33 pm

I recently changed the fuel pump on my M10, still running on the original Pierburg carb..
I got it from BMW as it's a manual pump, working of the camshaft.
Was about £120
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MyNameIsOllie
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Tue May 08, 2018 1:12 am

Brianmoooore wrote:No electric pump on these, so (shouldn't) be a pump relay to change.
Lift up the rear seat base, remove the oval inspection panel, and remove the tank level sender and pick.
You will now have the pipe that leads to the pump disconnected, so it will be easy to check if it is blocked or leaking, and be able to see if there is anything wrong with the pick up pipe.

P.S. Just typed all the above while still on page 1, without noticing that a second page had started, so apologies to 30316 for duplicating some of his post!
Oh okay, I was super confused about the fuel pump situation on these cars! So is it just one pump on the head and that's it?
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Tue May 08, 2018 7:26 am

Yes
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CR24v??? Where's it all gone?? LOL
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Tue May 08, 2018 10:01 am

Rav335uk wrote:Yes
Alright, that's actually good news. I'll fix this asap and post the results.

The lack of E30 316 documentation really surprises me, but I suppose everyone bought the 316i.
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Tue May 08, 2018 10:42 am

The 316i didn't come out till 1986 I think , as I have both versions.
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MyNameIsOllie
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Sat May 12, 2018 3:53 pm

Alright, so I've replaced the fuel pump and the fuel lines aren't blocked, but the problem remains. Now I'm looking towards spark or timing being the root of the problem. Any wisdom?
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Sat May 12, 2018 4:09 pm

Have you tried replacing the fuel filter? They can and do get clogged up after a few years...
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MyNameIsOllie
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Sat May 12, 2018 6:37 pm

Speedtouch wrote:Have you tried replacing the fuel filter? They can and do get clogged up after a few years...
Yeah replaced it last week
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