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Removed in tank pump and cleaned out the screen filter. It was fairly dirty. There are a couple remaining rubber lines in the back that I will replace as well as a new fuel filter. While waiting for parts to arrive, I will do another cleaning of the tank to ensure there is no crud left. That way I will know the tank, pumps, hoses and fuel filter are good and then work my way forward.
Got a new external pump as old one was starting to fail and now I have the following condition. New fuel filter and tank has been thoroughly cleaned. I am hoping you might help narrow down what might be the issue. Below is the current state after installing external pump.
Did a CCP test with the following results (valve closed):
53psi
51psi @ 10min
49psi @ 20min
47psi @ 30min.
After a couple hours it was still reading 30psi
When the pump is running the pressure gauge would pulse between 45-53. Pulses would stop after approximately one minute after turning off the pump and the guage would read 53psi.
With the valve open on the gauge, running the pump the fuel returning to the tank was extremely low. Checked the oil dipstick and don't see or smell gas on it.
When we open the hose at the wur outlet, fuel sprays out.
It seems like there is a blockage somewhere as it can build pressure but it seems to stay and not decrease at the right rate. CCP pressure is low, does that mean the internal pump isn't up to the task anymore or is it related to something else? Fuel distributer is a rebuild that was installed by me when I tried to get it running. WUR is an old rebuild prior to my ownership.
Does the pressure regulator in the fuel distributor come out easily. Should be able to remove the bolt and then extract it with a magnet. If it doesn't come out, it's rusted in place or stuck and will cause that type of pressure pulsing and the idle will surge repeatedly and not be stable.
I'd sort out the fuel flow issue before working on the pressures.
1. Check fuel flow from the pump to fuel distributor. A good place to check is the fitting on the passenger side of the engine compartment on top of the fender well. There are two fittings there. One supplies the fuel distributor and the second is the return to the tank. Might as well open them both. First check the flow from the pump to the engine compartment fitting. If you don't get sufficient flow at this fitting then you know your problem is between the tank and the fender. otherwise go to step 2
2. Undo the fitting on the side of the fuel distributor where the supply line enters. There is a strainer in this fitting. Check that it is not clogged. If it isn't clogged then re-connect this fitting and reconnect the supply fitting at the fender.
3. Check fuel flow at the return fitting in the engine compartment. If you don't get full flow then there is a blockage somewhere in the fuel distributor. The pressure control valve Petza referred to could be the issue. There are other possibilities as well if. If you do get full flow then go to step 4
4. With all fittings reconnected check the fuel flow leaving the WUR. There is a tiny strainer inside the inlet fitting that can plug up. Pressure up the system and crack open the line leaving the WUR and returning to the fuel distributor. There should be lots of fuel coming out. The WUR inlet comes off the top of the fuel dist. The WUR return line connects into the side of the fuel dist near the fuel return line to the tank
Report your results and we'll think of what to do next.
Does the pressure regulator in the fuel distributor come out easily. Should be able to remove the bolt and then extract it with a magnet. If it doesn't come out, it's rusted in place or stuck and will cause that type of pressure pulsing and the idle will surge repeatedly and not be stable.
I'm talking about this piece.
This part should come out freely with a magnet
From its port here
Petza914, the pressure regulator came out easily and essentially looks brand new.
Originally Posted by Cymadesign
I'd sort out the fuel flow issue before working on the pressures.
1. Check fuel flow from the pump to fuel distributor. A good place to check is the fitting on the passenger side of the engine compartment on top of the fender well. There are two fittings there. One supplies the fuel distributor and the second is the return to the tank. Might as well open them both. First check the flow from the pump to the engine compartment fitting. If you don't get sufficient flow at this fitting then you know your problem is between the tank and the fender. otherwise go to step 2
2. Undo the fitting on the side of the fuel distributor where the supply line enters. There is a strainer in this fitting. Check that it is not clogged. If it isn't clogged then re-connect this fitting and reconnect the supply fitting at the fender.
3. Check fuel flow at the return fitting in the engine compartment. If you don't get full flow then there is a blockage somewhere in the fuel distributor. The pressure control valve Petza referred to could be the issue. There are other possibilities as well if. If you do get full flow then go to step 4
4. With all fittings reconnected check the fuel flow leaving the WUR. There is a tiny strainer inside the inlet fitting that can plug up. Pressure up the system and crack open the line leaving the WUR and returning to the fuel distributor. There should be lots of fuel coming out. The WUR inlet comes off the top of the fuel dist. The WUR return line connects into the side of the fuel dist near the fuel return line to the tank
Report your results and we'll think of what to do next.
Cymadesign following your steps, update is as follows:
1. Fuel flow from pump to distributor is good at engine compartment. Prior to that, also confirmed the internal pump and external pump and after accumulator has good flow. So from tank to engine bay, good flow and no restrictions.
2. Thank you for pointing this out. I didn't know this strainer existed. The strainer was very plugged up. Soaked it for a week and it cleared right up. Strainer looks to still be intact and good condition. Last night proceeded to next step.
3. Flow rate at return is now good. Pulsing flow is also gone.
4. Opening line at WUR outlet, lots of fuel came out when cracking it open.
Valve open
WUR surface temp: 60F
CCP: 58psi
Adjust wur pin down
CCP: 27psi
WCP: 36psi (with 2 pin connected)
Proceeded to a/f baseline
11 turns to injectors squeal (guide says should be around 11-15)
approx 1/2 turn back (1/8 at a time) to stop squeal
Idle mixture baseline
was currently at 5 1/4 turns cw to baseline
set it ccw 3 turns (guide recommended 2-4)
Started engine (2 pin and wur vacuum hose disconnected)
Connect 2 pin 36psi
Connect wur vacuum 44psi
Engine runs and stays running. Idle screw was adjusted but still between 3-4 turns. Idle approx 750rpm. Revs smoothed out the more it ran.
Next week check the timing. Anything else I should be looking at?
Thanks everyone for helping out so far. One big step closer to getting it back on the road.
Update from the last few months. A leak started to develop at the internal pump. Even while carefully removing internal pump, it pulled the sleeve out of the tank. Got the repair from Roger and now have an upgraded external pump, tank repair sleeve, and in tank strainer. Set the timing. Flushed some more fluids. Put some injector cleaner in the tank and filled up the tank. Essentially all new lines and parts from tank to wur.
Took it on it first test drive in over a decade. Running intermittently rough. Sometimes runs decent, sometimes better, sometimes worse. Have taken in on 4 shorts drives to see if anything improves, worsens or stays the same. But results vary day to day. About 4 times when slowing down and going to downshift the engine just cuts off. No sputtering, no stalling indications. Similar to just turning to key to off position.
I have some new injectors on their way and will install once they arrive.
Making progress and have enjoyed the comments in my small town from little kids liking the car, to some grey hairs (no offence) at the gas station knowing what that it is an 928 and almost guessing the correct year.
If the injectors don't resolve it (I don't think they will) then the next thing I'd look at is the Fuel Distributor. At a minimum take each banjo fitting from the fuel lines off and remove and clean out the tiny screens in each port. If those are clogged with gunk from the tank, they can result in intermittent issues. Also remove the pressure regulator fitting and make sure the internal pin slides out (can capture it with a small pickup tool magnet) and make sure there's no gunk binding that up as it can change your fuel pressures.
If the injectors don't resolve it (I don't think they will) then the next thing I'd look at is the Fuel Distributor. At a minimum take each banjo fitting from the fuel lines off and remove and clean out the tiny screens in each port. If those are clogged with gunk from the tank, they can result in intermittent issues. Also remove the pressure regulator fitting and make sure the internal pin slides out (can capture it with a small pickup tool magnet) and make sure there's no gunk binding that up as it can change your fuel pressures.
Pulled the banjo fittings and there is no screens in the ports. Pressure regulator fitting is clean.
Replaced the injectors. Running a bit better. Checked the spark plugs they were a bit dirty but not too bad. Car starts and idles. But after warming up the idle pulses. Around 100rpm variance. Could it be a vacuum leak somewhere? Or are we still thinking distributor?
01-16-2023, 06:34 PM
