E9 running issues!!!!

[Boobouna]

Guys and girls I’m running out of patience. I’ve got a 73’ 3.0CS running original Zeniths. The car had not been driven for years so I went through and replaced almost everything mechanically including rebuilding the engine which was leaking from top as a result of overheating from prior owner. Rebuilt the carbs with W&N kit, and had a full service using full kit from W&N (new filters, cap and rotor etc). Rebuilt brake boosters, power steering rack, recored radiator etc. After all this was done I picked the car up from the mechanic and the following day went on a 200mile round trip to the mountains here is Sydney, Australia. The car ran perfect, didn’t miss a beat, flawless, I was ecstatic. Maybe two more drives after, the problems started to arise. The problem I have is when the car is warm/hot after 20min driving the car has issues when I stop at the lights. The revs start to drop and then it chokes and coughs at idle trying to stay running. I drive off from the lights sometimes to a bit of splattering then it drives, but issue continues every stop at lights. Then I get home and slowly park the car and it dies. So it’s been back and forth to my mechanic, in the beginning it was simple as blowing it out through the carbs with the thought it was just something blocking the carbs. It fixed the problem and then a day later same issues. Then we replaced the ignition coil and then noticed the carbs weren’t getting enough fuel so we replaced the fuel pump (W&N), still didn’t fix it then it got worse and couldn’t start the car. Found no fuel getting to the carbs, so unblocked the fuel lines then noticed there is rust in the fuel tank (not leaking). We cleaned it all out then prepped the tank and completed the process with sealer. Cleaned the tank pickup screen and off I went. Driving good on the way home then 15-20min later same problem. I don’t know what else to do, I’m thinking it may be carb related but not sure. Im dying here cause we have replaced almost everything!!
Really hoping someone can help. My patience has Run out.


Sent from my iPhone using Tapatalk

 

[Stevehose]

As lomg as the carbs have been cleaned out of any rust debris from the tank I would install a temporary electric fuel pump inline to see if that solves your problem of either vapor lock or other fuel starvation issue.

 

[stphers]

Get the engine hot and then check fuel pump pressure AND fuel pump volume It can have pressure but little volume. Specs are in the bluebook manual. Be carful checking the volume, you have raw gas ( maybe in this instance ) around a hot engine. I have fixed most of these issues with an electric fuel pump and check valve near the tank.

Thanks, Rick

 

[Boobouna]

As lomg as the carbs have been cleaned out of any rust debris from the tank I would install a temporary electric fuel pump inline to see if that solves your problem of either vapor lock or other fuel starvation issue.

One thing I should mention is I ordered a non-return valve with the fuel pump but my mechanic didn’t install it, said it didn’t need it. Not sure if that would have affected anything?


Sent from my iPhone using Tapatalk

 

[bluecoupe30!]

hmmm, fuel pump also has a screen that often needs cleaning. Have sometimes seen fuel line under drivers floor crimped from previous "insensitive" floor jack. I think you will solve this straight away as you have eliminated some of the obvious weak links. Good luck! Mike

 

[aearch]

YOU know get aset of webers problem solved
zenith are a ghost nitemare.

 

[Boobouna]

YOU know get aset of webers problem solved
zenith are a ghost nitemare.

Assuming it’s the carbs then yes problem solved. But I’m old fashioned and want the car the way it came from the factory. Pinpointing the root cause is the issue, is it carbs or is it fuel or is it neither.


Sent from my iPhone using Tapatalk

 

[HB Chris]

YOU know get aset of webers problem solved
zenith are a ghost nitemare.

Alan, once again you don’t know what you’re talking about.

 

[JayWltrs]

Assuming it’s the carbs then yes problem solved. But I’m old fashioned and want the car the way it came from the factory. Pinpointing the root cause is the issue, is it carbs or is it fuel or is it neither.

Sent from my iPhone using Tapatalk

Symptoms sound identical to problem I had with an old truck —debris wouldn’t stay out of the fuel system. After what sounds like many of your efforts, my mechanic ran engine with a rigged line from an external tank or cell; et voila — tank was either too far gone or the cleaner/sealer failed. New tank. More flushes. No more problems, until I accidentally hit the switch to an old reserve tank, promptly re-gunking the system.

 

[aearch]

yes good point
like above it must be starving for fuel

 

[Markos]

Symptoms sound identical to problem I had with an old truck —debris wouldn’t stay out of the fuel system. After what sounds like many of your efforts, my mechanic ran engine with a rigged line from an external tank or cell; et voila — tank was either too far gone or the cleaner/sealer failed. New tank. More flushes. No more problems, until I accidentally hit the switch to an old reserve tank, promptly re-gunking the system.

That's great idea. That's how I drove my car home from the seller. I didn't want to suck up old gas. It's not even rigging per se, and it is super easy. Just unplug your fuel line from the manual fuel pump. plug the line with an 8mm bolt. Plug your gas tank fuel line into the mechanical fuel pump. You want to use an outboard gas tank with a hand pump to prime the system, as seen below:

 

[Boobouna]

Symptoms sound identical to problem I had with an old truck —debris wouldn’t stay out of the fuel system. After what sounds like many of your efforts, my mechanic ran engine with a rigged line from an external tank or cell; et voila — tank was either too far gone or the cleaner/sealer failed. New tank. More flushes. No more problems, until I accidentally hit the switch to an old reserve tank, promptly re-gunking the system.

I considered a new tank but saw the price of a new one and considered other options. My tank wasn’t leaking so I didn’t feel the need to replace it, rather get it cleaned and sealed. I used the POR-15 fuel tank repair kit and it looked good when I finished with it. I will buy a new tank if that’s the problem but I want to make sure before I outlay all that money.


Sent from my iPhone using Tapatalk

 

[deQuincey]

Assuming it’s the carbs then yes problem solved. But I’m old fashioned and want the car the way it came from the factory. Pinpointing the root cause is the issue, is it carbs or is it fuel or is it neither
Sent from my iPhone using Tapatalk

you are so right, usual advice to swap zeniths with a poorer replacement is not exactly going forward, zeniths are the right stuff, you rebuild them, and they were right in the begining, so ok, they are not the culprit, something else happened later,...

from your explanations it seems that the debris might be all around the system, and that means making sure you have no more debris in the system

an antireturn valve is a very good thing to have together with a good filter and a pressure meter in the same line (after the pump), i can point you to my setup if i can find it, i can send you pics by email

i was unable to read which kind of fuel pump you have, the mechanical should work well, but wn replacements in this field are not exactly the best, we found some of the good pierburg stuff some years ago

unfortunately the debris might be in all the system and the carbs are very sensitive with tiny passages, youd better rebuild them again

p.s. did you used my videos ?

 

[Mal CSL 3.0]

I have quite a meaty aftermarket fuel pump on my engine. Seems to ensure no fuel starvation issues.

 

[Boobouna]

you are so right, usual advice to swap zeniths with a poorer replacement is not exactly going forward, zeniths are the right stuff, you rebuild them, and they were right in the begining, so ok, they are not the culprit, something else happened later,...

from your explanations it seems that the debris might be all around the system, and that means making sure you have no more debris in the system

an antireturn valve is a very good thing to have together with a good filter and a pressure meter in the same line (after the pump), i can point you to my setup if i can find it, i can send you pics by email

i was unable to read which kind of fuel pump you have, the mechanical should work well, but wn replacements in this field are not exactly the best, we found some of the good pierburg stuff some years ago

unfortunately the debris might be in all the system and the carbs are very sensitive with tiny passages, youd better rebuild them again

p.s. did you used my videos ?

I purchased my fuel pump from W&N but I didn’t look at it, just gave it to my mechanic to install. Going from the pic on the website it is a Pierburg. Worth mentioning the same issue was there with the old pump and the new one, so I’m thinking that possibly rules out the new pump.


Sent from my iPhone using Tapatalk

 

[deQuincey]

I have quite a meaty aftermarket fuel pump on my engine. Seems to ensure no fuel starvation issues.

View attachment 41873

your car is injection not carbuerted, cs has a mechanical pump in principle

 

[deQuincey]

I purchased my fuel pump from W&N but I didn’t look at it, just gave it to my mechanic to install. Going from the pic on the website it is a Pierburg. Worth mentioning the same issue was there with the old pump and the new one, so I’m thinking that possibly rules out the new pump.


Sent from my iPhone using Tapatalk

https://www.wallothnesch.com/en/vergaser-einspritzung/bmw-2-5-cs-3-0-csl-e9/katalogbild-13-13.html

this is the rubber membrane version, i found it not that good when compared to the metal mambrane sealed version
BTW it is a Fake pierburg version, this was long time ago commented, they are sold by pierburg in pierburg boxes, but they are NOT pierburg but an unknown italian brand,...

 

[Belgiumbarry]

your car is injection not carbuerted, cs has a mechanical pump in principle

deQuincey , Mal CSL ment ofcourse fuel filter... not pump. He has indeed a big filter there.

 

[deQuincey]

deQuincey , Mal CSL ment ofcourse fuel filter... not pump. He has indeed a big filter there.

i do not know really he might have the fuel pump place up there, but yes good point as the metallic injection filter is also not correct for carbs

 

[Ohmess]

Yeah, this sounds like a fuel delivery issue. The first thing I would do is to again go through and check the filters/screens in your fuel system including the little screens in the carbs (if Zeniths have them; I have Webers).

Next, I would look at your fuel lines. Normally it is unlikely that debris can get caught in the fuel lines, but I had a dented fuel line in my car near the rear subframe mount that I cut out and fixed after I fixed the rust in my tank specifically because I was concerned that something might get stuck in the lines there.

Also, I would take another look at the floats in your carbs. I don't have Zeniths, so I can't give you specifics, but one thing to consider is that the original data for our cars is based on gasoline that had a different specific gravity as compared to today's fuels. So the floats may be set to the correct original specification, but may act differently because the fuels we have to use differ from fuels in the 1970s. You may need to alter your floats to take the ethanol into account.