Nissan USA MP1F2A25LV:
Fuel System Diagnoses

Nissan MP1F2A25LV, P1F2-9H0249
Called out to customer location for a engine stalling issue. Arrived at customer location and spoke with the customer. Customer states he has been having runnability issues for a months. Another company prior to me, went out and rebuilt the nikki regulator. He was called back out for same issue a month later. The tech replaced the injector holder. Then 3 weeks later I was called. Inspected and found the fuel pressure sensor unplugged. There was an extra sensor plugged into the harness and was just hanging beside the injector holder. The unit runs like this for a minute then stalls. Let sit for 10 min and cranks and runs all day. I unplugged the extra sensor and plugged the harness connector back into the sensor mounted in the holder. The engine now barely runs and stalls when throttle is applied. Checked fuel pressure at regulator check port. I have 5 psi constant and holds when key is turned off. I have no codes popping up except for the E-36 when I unplugged the fuel pressure sensor with the ignition on. I don't understand how the engine runs better with a fuel pressure sensor not reading any pressure. This one has me stumped. Please help!
  • Posted 5 Jun 2014 03:58
  • Discussion started by LTS1
  • Florida, United States
Showing items 1 - 13 of 13 results.
ha ha right on...
  • Posted 6 Jun 2014 11:55
  • Reply by LTS1
  • Florida, United States
Everyday mah friend...........everyday!
  • Posted 6 Jun 2014 11:53
  • Reply by RCAV8TOR
  • Alabama, United States
Ha Ha Ha, well at least you have other units to swap parts with. Man 50 trucks? I bet that keeps you pretty busy.
  • Posted 6 Jun 2014 11:52
  • Reply by LTS1
  • Florida, United States
As i said just shoot a little in air cleaner with it running and see if she perks up. As far as inputs i have a few and knowledge i have very little but i seem to keep a fleet of 50 these things going LOL. One other thing to do is just for giggles, remove the main lpg injector after the unit has died from fuel being shut off at tank. get some good ole penetrating oil( the thin wd stuff) and spray the injector while turning over the engine. The injector will pulse and you should see all kinds of small black particles coming out. This will be a sign that the plunger in injector is probably galled and injector is scrap.
  • Posted 6 Jun 2014 11:46
  • Modified 6 Jun 2014 11:53 by poster
  • Reply by RCAV8TOR
  • Alabama, United States
Now that makes sense. I didn't think of that. I will replace the injector and let you know the results. I appreciate your input and knowledge.
  • Posted 6 Jun 2014 11:41
  • Reply by LTS1
  • Florida, United States
with no fuel pressure being sensed, the injector stays open longer through PWM. The injector if not operating correctly will cause the unit to try and compensate PWM to injector. Remember all you are seeing is the electrical pulse when looking @ injector pulse on dash. It doesn't know the if the injector is super glued shut or open...its just a pulse listed in microseconds. In other words it is telling the injector to open but the injector may not be on the same page with the ecm
  • Posted 6 Jun 2014 11:37
  • Modified 6 Jun 2014 11:40 by poster
  • Reply by RCAV8TOR
  • Alabama, United States
What i used to do all day now takes me all day to do.
I actually did that as well. Pulled the small hose that goes from the air horn to the regulator. Sprayed tiny amount of starting fluid, and the engine did perk up for a second. I didn't think this really had any meaning.
  • Posted 6 Jun 2014 11:34
  • Reply by LTS1
  • Florida, United States
you are ok on pressurer as i have seen them run in the high 20's. I am thinking you have an injector problem but do a juice spray as i recommended with engine runnibg and if it perks up then you almost definitely have an injector issue.
  • Posted 6 Jun 2014 11:32
  • Reply by RCAV8TOR
  • Alabama, United States
What i used to do all day now takes me all day to do.
Makes absolutely no sense to me how she runs better seeing no fuel pressure.
  • Posted 6 Jun 2014 11:31
  • Reply by LTS1
  • Florida, United States
.28 when its plugged in correctly. With the pressure sensor hanging it was reading.01
  • Posted 6 Jun 2014 11:28
  • Reply by LTS1
  • Florida, United States
Seems she is running lean. What was the lpg pressure showing on meter panel?.30ish Kpa? To check the o2 sensor, spay a little carb cleaner in the intake while running and see if it changes dramatic. If it does then i would almost say it is the main injector.
  • Posted 6 Jun 2014 11:26
  • Modified 6 Jun 2014 11:30 by poster
  • Reply by RCAV8TOR
  • Alabama, United States
What i used to do all day now takes me all day to do.
RCAV8TOR, I was hoping you would respond. Went back out today for troubleshooting. Replaced the regulator, still same problem. Pulled inlet tube out of injector holder and checked last chance screen. It was ok. Pulled the injector and inspected it. It is not new. The guy that replaced the injector holder probably has the new one, that Im told comes with the injector holder. The injector was clean with only small traces of tar. I put my ear to the injector while it was running and I could hear the injector pulsing. I took the boost injector out and put battery voltage to it, and it works fine. Put everything back together. Went into the on board diagnostic system. Checked to see if the O2 sensor was switching. It was stuck on lean.
Now this is with the pressure sensor hooked up properly. Put it back like I found it with the extra sensor plugged in and hanging from harness. Found with this set up that the O2 sensor was switching normally. Then I checked to see if the injector pulse was swinging. It was indeed swinging but I don't have specs as to what the parameter is suppose to be. I even tried the on board air fuel reset, with no luck. I was about to give up for the day, she was sitting there idling. Sounding like it was running on 2 cylinders and it stalls. I look at the display and find code E-43. From searching this forum I found that Cat has a bulletin out for this issue. Same symptoms. Injector pulse not right, not allowing ecm to switch from closed to open loop. Going to order the main injector tomorrow and see what it does. Let me know your thoughts.
  • Posted 6 Jun 2014 11:21
  • Reply by LTS1
  • Florida, United States
I would look hard @ the main injector as it seems to be all tarred up or is sticking. If the pressure sensor is plugged up and reading no pressure then the PWM or signal to injector is being turned on longer. After engine has ran for a minute then it could be turning the tar into a more fluid state and letting the injector pulse free. I wonder if the injector was replaced when the holder was changed? Check and make sure the wires for the sensor are not broken.
  • Posted 6 Jun 2014 11:03
  • Reply by RCAV8TOR
  • Alabama, United States
What i used to do all day now takes me all day to do.

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