W124 Can't figure out fuel pressure drop.

[Abstemious]

89 300TE m103. Car has sat for a good while for new head. Everything installed now but having issue with my FP immediately dropping from 80+ psi to +/- 27 psi. I put in new check valves on my FP's and have the accumulator line clamped, also new FP regulator... and still getting this immediate drop in FP measured at top chamber port. Also, I have my fuel lines off and am not loosing fuel out the top of the FD through the FI holes. What else could be going on besides the accumulator and the check valves? Are bad check valves out of the box reasonable possibility? Can these valves be checked manually off the car ? Any ideas here much appreciated.

[mpolli]

Have you measured the pressure at the output of the pump?

[Abstemious]

Originally Posted by mpolli

Have you measured the pressure at the output of the pump?

Hi, no just top port of FD and 85 or so there, that's just cycling pumps with key, did do a fuel volume delivery test too which passed. Would there be some benefit to measuring at the pump? Thanks

[optimusprime]

Pumps will loose pressure over night if they need replacing..But reading again i will plug for faulty FD .

[mpolli]

Originally Posted by Abstemious

Would there be some benefit to measuring at the pump? Thanks

If you measure no pressure drop at the output of the pump then that would indicate the problem is farther on. However I do not have any experience with mechanical fuel injection, only electronic so I am not much good with tribal wisdom on that. Just using basic troubleshooting approach.

[Frank Reiner]

Originally Posted by Abstemious

89 300TE m103. Car has sat for a good while for new head. Everything installed now but having issue with my FP immediately dropping from 80+ psi to +/- 27 psi. I put in new check valves on my FP's and have the accumulator line clamped, also new FP regulator... and still getting this immediate drop in FP measured at top chamber port. Also, I have my fuel lines off and am not loosing fuel out the top of the FD through the FI holes. What else could be going on besides the accumulator and the check valves? Are bad check valves out of the box reasonable possibility? Can these valves be checked manually off the car ? Any ideas here much appreciated.

Couple questions:
- What suggested that the pump check valves should be replaced, and have you tried re-installing the original valves?
- Which accumulator line have you clamped?
- What suggested that the fuel pressure regulator (FPR) should be replaced, and have you tried re-installing the original?

Cycle the pumps a few times, and then with the pumps off (and a rag over the FD if the lines are removed), open the air flow sensor plate all the way, and shine a light into the air guide under the FD. Is there a pool of fuel under the FD?

[Abstemious]

Originally Posted by mpolli

If you measure no pressure drop at the output of the pump then that would indicate the problem is farther on. However I do not have any experience with mechanical fuel injection, only electronic so I am not much good with tribal wisdom on that. Just using basic troubleshooting approach.

Ah yeah... worth doing, how to hook up... thanks.

[Abstemious]

Originally Posted by Frank Reiner

Couple questions:
- What suggested that the pump check valves should be replaced, and have you tried re-installing the original valves?
- Which accumulator line have you clamped?
- What suggested that the fuel pressure regulator (FPR) should be replaced, and have you tried re-installing the original?

Cycle the pumps a few times, and then with the pumps off (and a rag over the FD if the lines are removed), open the air flow sensor plate all the way, and shine a light into the air guide under the FD. Is there a pool of fuel under the FD?

Not yet, nothing seems to have changed with the new ones tho.

The rubber line on the smaller end of the accumulator.

Nothing really, just tried it as I had it around as it was purchased for a car that has been sold.



Ok tried the last part. No puddle that I can see down there. I did notice though, that I do seem to have some slow leakage at the fuel ports with the plate at resting point, play between lever and FD plunger, too. Also, I can't get fuel to gush out of the ports like they should... as the fuel pressure is dropping but still high enough to push fuel- I need to get a better understanding of what this all means. Btw, that harbor freight fuel tester I bought "fits", but man its absolute junk, I hope that's not another dang variable, at least the gauge itself seems ok. *Thank you.

[Abstemious]

Going to see what this feller has to say on the subject https://www.youtube.com/watch?v=xlxm6IR5ilM&feature=youtu.be

[Frank Reiner]

Ab:

Good that there is no puddle under FD; KE Jet metering plungers have a seal at the bottom to prevent leakage when shut off.
Slight leakage at the nozzle ports is normal; the nozzles have internal check valves.
Play between lever and plunger at rest is normal for KE.
The "new" FPR just might be the culprit.

[Abstemious]

Originally Posted by Frank Reiner

Ab:

Good that there is no puddle under FD; KE Jet metering plungers have a seal at the bottom to prevent leakage when shut off.
Slight leakage at the nozzle ports is normal; the nozzles have internal check valves.
Play between lever and plunger at rest is normal for KE.
The "new" FPR just might be the culprit.

Starting to look that way, will report back with what my advisor comes up with. Seems like a pretty nice offer, 10$ donation to his patreon get's his full attention. Thanks for the feedback.

[Abstemious]

SOLVED (mostly). Yeah, was the FD... good used one this time and works great. Now, lambda spot on, ALL new(ish) tune up parts, have a strange popping thru the exhaust in low gears above 3500 rpm, comes and goes. Perfect cold start, idle and power... just popping, like a lean miss. Thinking maybe another spectacular quality dist. cap is bad. Thanks for the heyulp.

[optimusprime]

Good i diod say this in post 4 .

[Ferdman]

Abstemious, recommend buying a Bosch distributor cap and rotor. You also may to consider replacing the ignition wires.