Mechanical Fuel Pump Testing

[Dick Steinkamp]

Regards the fuel pump. I went through this exercise a couple years ago. Read all that was out there. Believed there were some "copies" or substandard Pierburg units circulating. Was ready to move to some electric conversion. Then bought a new battery, replaced all rubber fuel line parts, installed check valve, put my "suspect" Pierburg back in place, and everything worked fine. In the past, my weaker battery could not summon enough fuel all the way to the carburettors, after a couple weeks of sitting, and the reduced power from extra long cranking on the battery, would lead me to think fuel pump was not working. I was wrong. Volts + new rubber hose + tight fittings + check valve = success. Hope you have same good fortune. Mike

Another point I think Mike makes is we do need to drive these cars regularly. They are happiest when we do. Batteries stay charged, gas stays fresh, carbs stay full. Regular heat cycles get rid of any water in the engine oil, transmission (and brake fluid). Our cars will thank us with reduced maintenance, fewer mystery problems.

 

[E3_UK]

I agree. I have purchased many OEM parts for my E39Touring, that had the brand ground off. I suspect it said BMW, but was being sold under the actual manufacturer name. Regards the fuel pump. I went through this exercise a couple years ago. Read all that was out there. Believed there were some "copies" or substandard Pierburg units circulating. Was ready to move to some electric conversion. Then bought a new battery, replaced all rubber fuel line parts, installed check valve, put my "suspect" Pierburg back in place, and everything worked fine. In the past, my weaker battery could not summon enough fuel all the way to the carburettors, after a couple weeks of sitting, and the reduced power from extra long cranking on the battery, would lead me to think fuel pump was not working. I was wrong. Volts + new rubber hose + tight fittings + check valve = success. Hope you have same good fortune. Mike

This could also be a factor with mine, should have considered this. My battery is ok under normal circumstances but perhaps isn't cranking fast enough to fill an empty system plus the temperature is low so battery will be taking a pounding. I'll do a load test on it to see if it's marginal. It's on a battery conditioner full time but that doesn't guarantee it's cold cranking capacity. I don't know the age of the battery as it was on the car when I got it. Is there a cranking rpm stated anywhere ?.

 

[E3_UK]

Another point I think Mike makes is we do need to drive these cars regularly. They are happiest when we do. Batteries stay charged, gas stays fresh, carbs stay full. Regular heat cycles get rid of any water in the engine oil, transmission (and brake fluid). Our cars will thank us with reduced maintenance, fewer mystery problems.

Fully agree however using it here on the winter roads it would rapidly deteriorate with the amount of salt laid down. They rotted quickly when new so I need to do what I can to preserve it.

 

[Markos]

Did my test and found my issue. Turns out I had a hole in my fuel line immediately upstream of my filter. That sectio is (very) old hose. Everything after the filter is new, but also braided.

First pass (video began well after attempt to start normally, so system was primed).

After diagnosis, I found a small hole. Diagnosis was attempting to suck fuel through the lines (the old fashion way). My extractor is full of motor oil. Confirmed no vacuum.

The culprit. I think folks like @HB Chris have warned against braided fuel line since it disguises issues. I don’t intend to use it in my restoration. The problem is only slightly visible from the outside. The big cuts in the hose are from the leak. The little slices are from my utility knife.

Second pass (Success!!!):

After some starting spray and some carb flames we have ignition. My garbage can took the brunt:

Not e3 related, but took it for a spin around the neighborhood. Such a silly juxtaposition...

 

[Stevehose]

the want is bad for that Momo wheel

 

[Dick Steinkamp]

Congrats! That 2 year old gas looks like heck. Compare it with my (semi) fresh in post #20. It is a pain in the butt to do, but it would be great if you could get that out of the tank and put fresh in.

Also, note the difference in cranking speed. Battery? Starter?

 

[Markos]

Congrats! That 2 year old gas looks like heck. Compare it with my (semi) fresh in post #20. It is a pain in the butt to do, but it would be great if you could get that out of the tank and put fresh in.

Also, note the difference in cranking speed. Battery? Starter?

I’ve already done that once. I yanked the whole tank out with 13 gallons in it. Then just poured it like a pitcher into three five gallon buckets.

Not sure if it is the starter or the battery. The battery is a few years old but abused. It is tended now so it could be the starter. I intend to replace it when the motor is out.

 

[HB Chris]

Weber carbs????

 

[Markos]

Weber carbs????

Me? Yeah. I hadn’t started my car since the summer of 2018. I’m not surprised it was a chore once I fixed (aka shortened) the fuel line.

I don’t want to hijack this thread too much. I got the fuel pump action video. It is amazing how sporadic the fuel flow is. I will be getting an electric pump when all is said and done.

 

[E3_UK]

So, new pump fitted, cranked for ages, not a drop. Removed the pump and used a screw driver to operate it, five or six pumps then got a healthy delivery. Pump back on and cranking gives delivery shown in the video. It doesn't look particularly healthy, and why will it not lift without being manually primed ?. I used my oil extractor on the inlet hose and after a couple of strokes on the pump the fuel flowed freely, indicating no air leaks between pump and tank. Still runs like a dog until long after the chokes are fully open, then suddenly it just smooths out and runs perfectly. Maybe nothing to do with the pump, but still a bit of a mystery.

 

[Dick Steinkamp]

Your fuel looks worse than Markos' . That might be your bad running problem until the engine gets warm and can burn that (what looks like) old fuel easier. I think
gasoline is good for about 3 months and after 6 months or so it is pretty much varnish. Try feeding the pump with some fresh gas from a remote tank.

The pump volume does look weak. It is certainly enough fuel to run the engine under all load conditions, but it may not have enough suction to lift the fuel from the tank to itself without being primed. The volume problem must be the mechanism that operates the pump.

 

[Stevehose]

Time to try the insulator sanding trick? Maybe reduce by 2mm or so?

 

[stphers]

Hi Went back thru this post right from the start and I know people have asked about the condition of the pushrod but did not see any reference to it as the condition of it as well as the condition of the lobe on the cam I have seen lots of pushrods worn Also when we installed new fuel pumps, we would fill the cavity for the pushrod in the pump with grease

One more question, what is your fast idle speed when starting engine cold? Are you pushing the pedal all the way to the floor ( I actually do this a couple of times to squirt a little extra fuel into the manifold for cold starts ) in order to set both the choke and the fast idle?

There is a complete procedure to set chokes and fast idle speed on each one separately and then to make them work together Have done tons of these carbs and usually don't have any starting issues The warm up stage is always challenging And the final tune has to be done after all your ign system is set up properly Timing and ilde speed / mixture really work hand in hand

 

[Markos]

Your fuel looks worse than Markos' . That might be your bad running problem until the engine gets warm and can burn that (what looks like) old fuel easier. I think
gasoline is good for about 3 months and after 6 months or so it is pretty much varnish. Try feeding the pump with some fresh gas from a remote tank.

In defense of my 2yo gas, my car ran like a top when I took it for a spin. Based on the zombie show “The Walking Dead”, gas should last at least six years.

 

[E3_UK]

Thanks. No doubt a combination of all of these factors. At least pump wear is now eliminated. Fuel is probably 3 months old at least. I did reduce fast idle previously to around 1200 as i didn't like the top end rattle it had at the factory setting until oil pressure got to the cam after a second or two, so probably too slow for winter cold starts. Think I'll leave it until springtime now and will suck the old fuel out before running it again. No doubt the pump stroke is reduced due to cam and pushrod wear so reducing the insulator thickness is still an option or fit a new rod.

 

[duct-tape]

gas should last at least six years.

it can be stabilized too

 

[Markos]

it can be stabilized too

Sorry that was a joke related to how unrealistic the fantasy zombie show is.

 

[duct-tape]

Sorry that was a joke related to how unrealistic the fantasy zombie show is.

my wife has quoted me for criticizing the availability of fuel in many post Apocalypse movies/shows.
EVs and bikes are the only reliable mode of transpo after like 5 years in.

 

[mulberryworks]

my wife has quoted me for criticizing the availability of fuel in many post Apocalypse movies/shows.
EVs and bikes are the only reliable mode of transpo after like 5 years in.

Well, how many cycles are you going to get from those batterie packs? And I don't think that you'll find many good ones among the abandoned cars after 5 years.
Of course, the same goes for tires and since there are fewer full size spares being sold these days they would have to find a tire store and do the mounting themselves.
And where are you going to charge this EV? Unless you can find someone who's already set up to be off the grid or has a proper disconnect box setup with their PV solar array you won't be able to get power. By code, all PV controllers will turn off when the grid goes down so that you aren't putting power onto lines that are down and potentially endangering linemen who repair the grid. Of course if you are savvy, you could change this, but that's certainly not a given, except for TV shows of course.

I guess after the bikes wear out we'd be back to horses and donkeys.

 

[duct-tape]

I've built solar setups and know how to build/run capacitor duplexers so I'm more confident in my own ability to run electric, but yes -all valid.
maybe after 10 years, we can go back to farming whale oil, or i suppose I could learn how to make hemp oil