Hi all,
I am new to this site but have been a 7.3 owner since 2013, I have a 1998 1/2 E350 7.3 with frame mounted fuel pump. The only engine related work I have had to do is a fuel bowl rebuild when I first bought it. Mileage is now 258k and had started running a little rough recently then about a month ago when I was trying to make it up a hill I drive up frequently it lost all power, so after much research I put a fuel pressure gauge on it and it was very low under 40psi.

I dropped the tank and as expected the screens were very clogged with tank delamination. I cleaned out the tank, then pressure was a steady 65psi at idle and would drop to around 60psi under load. The engine still had no power though and vibrated a bit when I revved it.

I did an oil change (it had been a while like 5k miles) air filters were pretty bad and replaced them as well as fuel filter but when I test drove it after new fuel filter the gasket hadn't set right and lost all my fuel pressure again. I limped it home (under a mile) and reset o ring with no leaks now. Also no smoke other than when really cold out which it has done in the past. When I really step on it quite a bit of black smoke but I usually don't run it that hard.

I did have black soot coming out of my down pipe to turbo flange so I removed and carefully sanded the flange which had carbon buildup keeping it from sealing. Seams to have helped with exhaust smell and soot hasn't returned yet.

Next I did the injector wiring resistance test from the IDM connector and all injectors were 2.8-3 ohms as well as a Buzz test using car gauge app. Buzz test did not bring up any codes and all pulses sounded fine. I also cleaned out the exaust back pressure tube and sensor.

Next day It was idling for a while as I was testing temperature ranges at each cylinder then revved up the engine and it seemed to return to normal power. So I drove it around a few days on short trips and most of the power was back with the exception of a slight hesitation and started noticing an intermittent popping or pinging sound as rpms increased. This sound reminded me of bad timing issue so replaced the old ford gray cps with new gray ford cps with no real change in performance.

I decided to add some Diesel Kleen in the tank to see if that helped any. Not long after one night it totally bogged down again and barely made it home (fuel pressure remained steady this time). Checked fault codes with car gauge pro and torque apps . Car Gauge showed some IDM codes p1670 and p1668. I don't have a 104pin break out box to test that fault so I was hoping maybe when I unplugged the IDM to check the injector wiring resistance it may have set those codes off, I tried clearing them and p1670 returned once more (but now doesn't). Also buzz test sounded worse after this happened. Should I invest in a 104pin break out box to do pinpoint tests or be satisfied that IDM codes aren't returning?

Next I removed VC on both sides and UVCH plugs are tight. When I unplug each injector motor vibrates noticeably so seams like they are all firing. When I unplug number #7 it seams to quiet the spark sound some but not totally. Also oil spouts seem to be flowing but can't totally be sure because of how difficult it is to see in the vans engine compartment.

From my research thus far I thought I may have damaged my injectors when fuel pressure dropped initially from tank restriction and then after fuel bowl filter gasket failure so I was planning to start replacing injectors but they all seem to be contributing when I unplug them, could this sound be coming from the motor internally or is it simply air passing through injectors? I might want to weigh my options before spending money on injectors and mods if engine just has to come out anyway.

I have limited funds to throw at this so I am trying to move strategically forward and rule out as much as possible in case I do have to wave the white flag and surrender it to a diesel technician. Would investing in a compression tester be a good next move. I didn't notice any blow by pressure out of oil filler cap before VC was removed just smoke.

This is my only registered "working" vehicle and happens to be my work van so I have had to postpone some jobs until fixed.

Thanks,

 

Hello,

In case any one has run across this sound before here are a few videos I posted on youtube of the motor running with VC off. The sound appears a few minutes after motor is started and as it warms up gets progressively worse. I managed to do a Buzz test and CCT with FORscan and got p0278 #6 balance fault from cct and p1277 #7 to high or too low from buzz test. Also the fuel pressure gauge is at a steady 65psi at idle but the needle does flutter a bit if that matters. Could this spark/popping sound be air in the lines? I did disconnect lines to remove tank recently and read about the quick connects sucking air in. My plan is to do the in tank mods with a new spectra tank and get rid of the quick connect hoses but hate to spend the money on that now if motor needs internal work. Any ideas or suggestions?

 

My only thought is maybe a loose injector hold-down.

 

Thanks for the response 88' E350 ,

Yeah, thats a thought I think I have read somewhere they can loosen up and make a lot of noise. I also just saw a video of a failed upper o ring with oil rushing out of the top of the injector bore which made me wonder because theres a bit of oil splashing around with the covers off. Do the spouts splash that much or could that be the start of o ring failure? will have to look more carefully where the splashing is coming from. Just looked up the torque specs for the injector hold down bolts. Shop manual says 11ft lbs or 132 in lbs, that sound right? I am kinda skeptical about what the manual says in relation to torque specs cause I once broke off a water pump bolt from what the manual indicated and found out later it was editing error,

Today I decided to put a clear hose between my tank and pump. It looked like carbonated diesel rushing through with lots of air bubbles (when I just put the clear hose into a 5 gallon can it came out clear with no bubbles) somethings brewing in my tank! I am wondering if I didn't reinstall the screens properly in the pick up tube, or maybe the pick up foot fell off. I was in a rush to get it back on the road so I could finish a job, definitely possible. Before I get too excited though I want to drop the tank again this weekend and make sure the clear hose I just installed isn't leaking somewhere and clamps are tight.

Is it possible this aerated fuel could be causing the popping sound and rough acceleration? The sound takes a while to show up when I first start it cold. I was thinking maybe over night the air bubbles might be leaving the system then the pump just starts the process again and they eventually return to the injectors?