moalaska Posted May 13, 2020 Report Share Posted May 13, 2020 Truck suddenly started bogging running bad, barely got it home. Compression check good. Put new spark plugs. Fuel pressure test, it's like 17psi, and as soon as it shuts off it drops to 10. If I pinch the return line and get it up to 60psi, it idles decent. 1 Quote Link to comment
datzenmike Posted May 13, 2020 Report Share Posted May 13, 2020 Partly clogged fuel filter? Running pressure should be in the mid 30s. 1 Quote Link to comment
moalaska Posted May 13, 2020 Author Report Share Posted May 13, 2020 1 hour ago, datzenmike said: Partly clogged fuel filter? Running pressure should be in the mid 30s. Changed it already, made no difference. 1 Quote Link to comment
datzenmike Posted May 13, 2020 Report Share Posted May 13, 2020 Well that leaves the FPR I guess. 1 Quote Link to comment
moalaska Posted May 13, 2020 Author Report Share Posted May 13, 2020 4 minutes ago, datzenmike said: Well that leaves the FPR I guess. Would a leaking injector cause a problem? I would imagine it would have to be leaking pretty bad for the pressure to drop below spec 1 Quote Link to comment
datzenmike Posted May 13, 2020 Report Share Posted May 13, 2020 The pump can provide for high RPM full load so I think not. Try giving the FPR a little rap with something. I'm surprised that it ran on 15 PSI 1 Quote Link to comment
moalaska Posted May 14, 2020 Author Report Share Posted May 14, 2020 I read this on a tbi conversion forum. "Okay, here's the rub guys. In 1986 for one year and only on the 720, Nissan's TBI in the Z24i ran about 14psi. We matched all harbody parts (injectors, ECU, regulator) and the truck ran fine at 38psi. When swapped to 720 TBI parts, (injectors, ECU, regulator) it ran fine. Mix and match any and you have drivability problems. So lesson learned, make sure if you have a harbody setup you use hardbody parts, and with a 720 720 parts.BTW, MIke can I get a copy of that as a PDF from you?" 1 Quote Link to comment
moalaska Posted May 14, 2020 Author Report Share Posted May 14, 2020 7 minutes ago, moalaska said: I read this on a tbi conversion forum. "Okay, here's the rub guys. In 1986 for one year and only on the 720, Nissan's TBI in the Z24i ran about 14psi. We matched all harbody parts (injectors, ECU, regulator) and the truck ran fine at 38psi. When swapped to 720 TBI parts, (injectors, ECU, regulator) it ran fine. Mix and match any and you have drivability problems. So lesson learned, make sure if you have a harbody setup you use hardbody parts, and with a 720 720 parts.BTW, MIke can I get a copy of that as a PDF from you?" I was getting 14-17psi when testing. so either this is true, or its not and my pressure is low. 1 Quote Link to comment
datzenmike Posted May 14, 2020 Report Share Posted May 14, 2020 I noticed that the D21 Hardbody Z24i parts are also different than the Z24i 720 1 Quote Link to comment
moalaska Posted May 14, 2020 Author Report Share Posted May 14, 2020 The Part number on my regulator is MPDB36-4. doing google search brings up a couple listings, some of which are for pathfinder, so im wondering if that info about the pressure was bogus. I found looking on nissan parts site, nissan number for mine is 16240-2G00, and 87 pathfinder is 16240-03g15. 1 Quote Link to comment
moalaska Posted May 14, 2020 Author Report Share Posted May 14, 2020 1 minute ago, moalaska said: The Part number on my regulator is MPDB36-4. doing google search brings up a couple listings, some of which are for pathfinder, so im wondering if that info about the pressure was bogus. I found looking on nissan parts site, nissan number for mine is 16240-2G00, and 87 pathfinder is 16240-03g15. its different part number on nissanusa site, but on factorynissanpartsonline, its same part number for pathfinders and 720. So it may or may not be, thats all I can conclusively say 1 Quote Link to comment
moalaska Posted May 14, 2020 Author Report Share Posted May 14, 2020 3 hours ago, moalaska said: its different part number on nissanusa site, but on factorynissanpartsonline, its same part number for pathfinders and 720. So it may or may not be, thats all I can conclusively say I'm pretty sure my truck is supposed to run at 37psi. A pair of vice grips on the return line told me so. I was able to drive down the street and back like that. I'm wondering, is this a rising rate fpr or static? 1 Quote Link to comment
moalaska Posted May 14, 2020 Author Report Share Posted May 14, 2020 I cannot find a fpr anywhere. I think my only option would be to put an adjustable fpr on, or convert to Weber. Insane that this part is unavailable. 2 Quote Link to comment
datzenmike Posted May 14, 2020 Report Share Posted May 14, 2020 37 PSI sound reasonable. The EFI system compensates for higher or lower pressure by adjusting the on/off rate of the injectors with feedback from the O2 sensor. 16240-12G00 is also used on the Hardbody and the Pathfinder. 16240-0g315 is just a superintendence number, the Z24i in the 720, D21 Hardbody and the WD21 Pathfinder use the same FPR. Well actually it's 16240-12G01 which is probably a different supplier or a sub part supplier or a part that was changed to plastic or is an upgrade, but has no effect on running. NOTE: the 16240-12G01 is also used on the VG30 engine through '88. 1 Quote Link to comment
moalaska Posted May 14, 2020 Author Report Share Posted May 14, 2020 Unfortunately all those parts are discontinued with no available stock that I can find. 1 Quote Link to comment
datzenmike Posted May 14, 2020 Report Share Posted May 14, 2020 Find one in a wrecking yard. Start a want ad in our classifieds. Someone may know where one is and send it up to you.. 1 Quote Link to comment
Charlie69 Posted May 14, 2020 Report Share Posted May 14, 2020 This is why I convert all the Z24Is to Weber the parts are not available it is much easier to work with the Weber than the old Nissan TBI stuff. 2 Quote Link to comment
McFerg Posted June 2, 2021 Report Share Posted June 2, 2021 (edited) On 5/13/2020 at 9:55 AM, datzenmike said: The pump can provide for high RPM full load so I think not. Try giving the FPR a little rap with something. I'm surprised that it ran on 15 PSI Hi y'all. What is the FPR...? Fuel pump regulator/The Electric Fuel Pump? is it the circular silvery part on the side of the carb? Edited June 2, 2021 by McFerg added insight 1 Quote Link to comment
datzenmike Posted June 2, 2021 Report Share Posted June 2, 2021 Fuel pressure regulator. On 5/13/2020 at 12:54 AM, moalaska said: Truck suddenly started bogging running bad, barely got it home. Compression check good. Put new spark plugs. Fuel pressure test, it's like 17psi, and as soon as it shuts off it drops to 10. If I pinch the return line and get it up to 60psi, it idles decent. By pinching the return line you are defeating the FPR so if the pressure goes up then the pump isn't at fault. I don't know where the FPR is on the electro injection Z24i. I do have it for the D21 Hardbody Z24i and it is on the same side as the throttle position sensor. Pressure should be about 36 PSI. 1 Quote Link to comment
McFerg Posted June 2, 2021 Report Share Posted June 2, 2021 Mike Is this it? https://www.instagram.com/p/CPm1lzHBT92/?utm_medium=copy_link 1 Quote Link to comment
datzenmike Posted June 2, 2021 Report Share Posted June 2, 2021 That's the choke unloader on a carburetor. 1 Quote Link to comment
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