Here's one to get you scratching your head.
I did an engine swap into my 1985 GMC S-15 Jimmy
and its been an ongoing project for about 3 years now.
the past year I've finally been able to daily drive it.
well about 5ish weeks ago something happened I was going about my usual day and all of a sudden it started acting as if the fuel were gelled or out of fuel "was about 5 degrees". Anywho I got the truck home after countless cranking and it seemed like it was running on 3-4 cyls. So I had towed it to my shop and had speculation on a faulty Lift Pump. So I went and Rebuilt the LP and the Injectors and put DN0SD265 nozzles in instead of the SD240's. I also replaced my fuel sender and replaced my rubber fuel lines.

Well i figured my fuel problem was fixed by the way it ran after the rebuild.
But once I took it for a test drive it took 8 miles and then it started doing the same thing. It was about 50 degrees. so the fuel is definitely liquid.
and today i took another test drive after stretching that one spring on that fuel valve on the side of the injection pump. so that didnt fix the issue either.

so im completly at a loss now I'm almost to the point of sending this BOAT ANCHOR to the Junkyard.

Any help is greatly appreciated thanks.

Have you changed the fuel filters?

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.

X2 on changing the filters. If it hasn't been run for 3 years I'd open the old filters and have a close look at the contents. The fuel tank could be a real mess after sitting three years.

I'll give 50 bucks for the engine if you want to sell it.

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84 300SD
85 380SE
83 528e
95 318ic

sorry i had forgot to mention that it already has a fresh filter and oil change.
and its been running strong ever since it came from the factory it was my daily driver before my wife crashed the car then i took the drivetrain and swapped it to the GMC because i wasn't smart enough to wire up the BMW M3 drivetrain i had in it.

I just havent experienced these issues in the past 4 years.

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Any chance your shutoff circuit is self activating slowly? Perhaps pull the vacuum hose for a test. Eight miles is too low for a tank vacuum problem I think.

My vacuum circuit is all on its own system hooked up to a toggle switch and an evap solinoid. Today I was told by an injection shop to monitor the fuel pressure going into the IP as I'm driving it. So once I get the delivery valves back together and in I'll test that.

Another possible cause: vacuum build-up in the fuel tank. When you get the poor running symptom, try removing the fuel tank cap. If you hear a "whoosh" and then it runs fine again, that's your problem: fuel tank venting.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Yea my grandfather told me to do the same thing and that didn't cure the system either
Unfortunately

Getting an accurate fuel pressure reading is a real trick. When I added a fuel pressure sensor to my engine data monitoring system Adding a Fuel Pressure Gauge, it took many iterations to get a decent reading. In the end I used both a snubber and a damper as well as software smoothing to get a usable reading. The problem is that the fuel pump is a positive displacement pump and cycles between very high pressures and almost no pressure several times a second. Many people report that the pulsing pressures can trash a gauge (and possibly an electronic sensor as well) so fluid filled mechanical gauges are the very minimum. There's no damper at all on the system so be prepared to use some pretty agressive means to smooth the pressure. Just for the record I was getting between 8 and 14 before stretching the overflow spring and now get between 18 and 25 depending on conditions. I've got it dialed in pretty well, but my damper (closed cell foam coated with silicon) is only good for several months before the element needs to be renewed.

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• 380SL (diesel)
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• Auburn Boattail Speedster replica

Alright great thanks for the advice.

Alright well an update on the issue.
I had went and soaked my delivery valve assemblies in a strong degreaser that I mixed up and scrubbed them with a brass wire brush and installed them.
After replacing the Alternator again I had taken it on a test drive tonight and got up to 10.5 miles without any problems what so ever.
And it's still running on 5 cylinders.
So could the delivery valve assemblies be what caused the issue?

Probably not. You want to disable your vacuum system to the shutoff valve on the injection pump. Temporarily plug the line if your brake booster system is on the vacuum system. Something strange could be happening that allows vacuum to develop in that circuit after awhile.

Just hook it back up to get shutoff activation after a test. Your getting 10.5 miles is not a signifigant thing.

I am sorry that I was not a little clearer early. Eight miles is not far enough to have a tank vacuum problem is what I meant. Also the condition of the fuel has to be always considered in these strange things. Not just the delivery.

My electric Vacuum shut off valve has two holes drilled in it to release pressure.
When I flip the switch there is enough vacuum to cut it out then I turn off the switch and the pressure is released. So there is always atmospheric pressure on the vacuum cut off when running.

Hit 32 miles tonight and no problems.
Thanks for the help I appreciate it.

Hit 32 miles tonight and no problems.
Thanks for the help I appreciate it.