Need help with fuel delivery

[rgafitanu@gmail.com]

Again you are right Tyler, I saw that but I thought it was draft for easy cast removal. Too many years since the hydraulic class and the cavitation. I guess that's why they call it german engineering if they designed it with cavitation prevention in mind. The problem is that I don't know which way is the right way, I took this pump apart 4 times and the impeller is scored on both sides. I got a used pump from ebay so I will have a spare.
I checked the battery with engine off 12.6V, at idle and 2000 rpm 13.9V, and 13.6 with headlights on. I think the charging is good. I don't know what alternator I have so maybe I should upgrade to 55W.

[Tyler S]

If you look at the impeller both sides you should see an area that has a lot less wear near the ends of the vanes. This is the area that passes over the ports and thus gets installed facing the motor. If theres enough wear that you cant see this its most likely worn past being usable. The impeller also has a "step" in the center that rides on the housing on both sides. If this step is gone then it needs to be replaced.
That voltage sounds alright. Sometimes overlooked is the main body ground cable and the body to engine ground strap. You can do a voltage drop test with modified volt meter leads (make them longer) make sure you have the same voltage potential at the back of the car where the pump and taillights ground to the body. Also the power to the pump. You do this test with everything on. Google "voltage drop testing". Lots of good explanations on how to.

[rgafitanu@gmail.com]

So here what I did next. I got a cheap pump from eBay but the bellows seal leaks and I tried soldering it but it's not holding and the pump leaks. I will keep it for parts, at least the drive washer is in good condition. Meanwhile I verified the orientation of the impeller on my old pump. Then I went on doing voltage measurements.
At the pump terminals, engine OFF, pump connected, 9.5V. That's 3V drop from the battery.
At the fuse same conditions, 9.5V, so the drop is not on the wires going to the back.
At the pump terminals, engine OFF, pump disconnected, 10.5V, so something else is sucking 2V and the pump accounts for only 1V drop.
At the pump terminals, engine ON, pump connected, 12.5V, confirming something else is sucking 1V now when the alternator is helping to 13.8V at the battery.
On that circuit I have the coil and the alternator and since the coil is a couple ohms I am assuming that this is the big consumer. Other than that the pressure is quite stable at 9 - 9.5 PSI with the old pump and the eBay pump.
I am thinking that the 9 PSI is dictated by the IP outlet check valve and since I cleaned it with compressed air I must have made it open sooner and I never get to the 11 PSI. Maybe I should leave it and just watch the gauge to clean the screen every few tanks, when I pulled it out the screen had some stuff in it already. I would like to put one of those glass filters with easy to clean elements before the pump but they caution against using it in fuel injection and I do not want to restrict my pump feed further.

[ja17]

How much pressure do you have when the return line is clamped-off?  Those little glass filters may not handle the volume of fuel, or the pressure, that is why they are not recommended for FI.  You can use a large in-line filter from an EFI 450SL, Datsun 280 Z or such. These are rated for FI and are large enough to handle the volume.

[Tyler S]

That is a serious voltage drop! The max I would ever want to see is around a tenth of a volt. With your different readings with the car running and not running it sounds like you have more than one resistance problem in the circuit. It will affect the other components as well like the coil. Even if items are "sucking power" it should still generally match the battery voltage, whatever that may be. Where are you connecting your negative test lead? Connect it at the battery and then on the chassis and see if you get the same reading. That way you can rule out a grounding problem. You may want to check the resistance of your ignition switch to start with. Then possibly the wire that runs from the alternator to the fuseblock. Start there.

Your original problem of the car quitting after 30 minutes may be coming to light. A bad wiring connection somewhere.
Tyler

[rgafitanu@gmail.com]

A couple of days ago as I was driving it and I saw the fuel pressure drop below 7 PSI. I got it home to sort once and for all this voltage/pressure drop. I checked and rechecked all + lines from the battery downstream and cleaned all ground points with no results, could not find where the 3V were disappearing. I was about to check all the loads like the coil and the others. Then I thought that I should check the home made switch: a 12' 120V power cord with a switch at one end and clamps at the other that I was using to power the pump while under the car. This cord was sucking the 3V.
I tossed it in the garbage but the pressure was still 7PSI. The pump inlet screen was not clogged, I cleaned it anyway but the pressure would not go above 8 PSI. With the fuel return clamped the pressure would go up to 13 PSI so this should be a sign that the pump is healthy. I replaced the fuel filter, the jar had very fine dark deposits on the bottom. The pressure got up to 9.5 - 10 PSI. So the tank is shedding and the pump screen is not catching the fine stuff. I will put a glass filter between the tank and pump intake but I will keep the fuel pressure gauge as well. I am chasing the elusive 11PSI that everybody has but I think that the IP outlet check valve opens sooner and I am not getting to the 11 PSI. I am not sure if there is a replacement for the check valve fitting, I could not find a Part# in EPC maybe somebody will sell a damaged IP for parts.

[ja17]

How is your main fuel filter and the drain plug screen in the tank?

[Tyler S]

It sounds like you solved one of the issues. Voltage to the pump. (I still dont like seeing a 1 volt drop)
Be carefull about adding an in-line filter as these are not designed for the high volume that the system circulates. It can become saturated very quickly. If your at 10 psi with a new filter and good voltage to the pump then theres not much more to do. Replacing the filter most likely fixed the pressure drop issue. The only other thing would be the pump itself. You may try your other pump one more time since you have fixed other issues. See if your pressure goes higher. If it remains the same then look into the IP relief valve.

[rgafitanu@gmail.com]

I would really like this to be the conclusion to the fuel problem. After another couple of hundred miles the fuel pressure started dropping again almost to 4 PSI. I got the car back on the lift, checked the fuel filter and it was clean. Drained the fuel and pulled the tank screen, it was clean. I removed the pump and mounted the generic pump getting everything running again. The pump screen had a lot of fine rust in it. I cleaned it and this time I swapped the bellows seal to the pump that I got from eBay and back on the car. Finally I got 10.5 PSI. So my original pump was a little weak, there is nothing wrong with the IP pressure relief valve and my tank is shedding. This is my second tank, the first one I took it to a radiator shop in Worcester MA for boiling but I ended up with a leak at the seam and that didn't stop the clogging. I am reluctant to do another cleaning and I don't want the coating to obstruct any flower pot passages.
I got a glass filter before the pump. I am using this filter because it's more convenient to replace the element than removing the pump to get the screen out. I also hope that I can see clogging through the glass.
Interesting note: the car runs with fuel pressure of 5 PSI although I didn't drive it too long in this condition.

I took it today for a mile to the grocery, the pressure dropped to 3 PSI and stalled. The glass filter was black. I got it back on the lift and removed the filter. The pressure is back at 10.5 PSI but this means the black stuff from the tank is getting now in the pump screen or the filter.
I would like to find a new tank and I tried a few German suppliers but no luck. eBay.de lists them at €2,000.
Anybody has a source for something reasonable or maybe a tank cleaner business that is familiar with the flower pot tanks?

[Naj ✝︎]

I got a glass filter before the pump.

May I know which glass filter you are using?

naj

[Jowe]

I would like to find a new tank and I tried a few German suppliers but no luck. eBay.de lists them at €2,000.
Anybody has a source for something reasonable or maybe a tank cleaner business that is familiar with the flower pot tanks?

Maybe this?: http://www.sls-hh-shop.de/230-280SL-R113/47-Tank/?_artperpage=10&listorderby=oxstock&listorder=desc

Ahh, you have a 111. Sorry, this may not fit...

[Jordan]

I would like to find a new tank and I tried a few German suppliers but no luck. eBay.de lists them at €2,000.
Anybody has a source for something reasonable or maybe a tank cleaner business that is familiar with the flower pot tanks?

Have you tried the Classic Center for a fuel tank?  That is where I got mine a few years ago and they were certainly a lot cheaper than €2,000.  I don't know what they are these days.  Once I replaced my tank it solved all my fuel delivery issues.

[rgafitanu@gmail.com]

Naj,
Attached is the glass filter. Most likely it has a very fine mesh otherwise it would not have gotten black in a matter of minutes. I will try the Classic Center next to see how much they are.

[Jordan]

If you are a member of the MBCA, which you hopefully are, you should get a 15% discount, or something along that line.  Make sure you tell them (Tom or Woody).