L98 cold start issue - FPR diaphragm - ???
08-11-2014, 06:33 AM
#1
Race Director
Thread Starter
L98 cold start issue - FPR diaphragm - ???
I posted this on an older thread, but since I wasn't getting any response, I deleted that post, and thought I'd start a new thread.
I should have known better, but a while back I bought a fleabay, cheap-o, pressure regulator diaphragm, and now have somewhat of a cold start problem on my 90. seems I have to crank 3 or 4 seconds without a start. usually, it will start on the second try - sometimes third. I've been recovering from a knee replacement, and finally got around to putting a pressure gauge on the thing. key on, pressure to 42 psi, after a couple seconds, a drop to 40 -- so far, so good, but it continues to drop. after 10-12 seconds, a drop to 20 psi, and it continues to around 10 psi after 32-34 seconds. at idle, I'm holding about 38 psi, and with revving the engine slightly, it fluctuates between 38-40 psi. upon shutting the engine down, a drop to 20 psi after 7 or 8 seconds, and 10 psi after 30 seconds. the injectors are new (well, rebuilds) boschIII's from FIC, so I'm fairly sure it not a leaking injector issue. I pulled the vacuum line off the FPR, and there was no signs of leaking fuel. I need to run out today to get a couple (fuel line) clamps for further testing, but my gut feeling, it's the FPR diaphragm. I did not have any starting issues prior to installing the diaphragm and injectors. the car seems to run fine otherwise. hot/warm starts - perfect. there was an older thread about defective FP diaphragms, and I'm thinking my problem may be related. what has me stumped, is when I hit the key, and the engine is cranking within those first two seconds, the rails are pressurized at 40-42 psi, oil pressure should be high enough for the start sequence. seems to me, it should start - ??? based on my initial fuel pressure readings, any comments?
WVZR-1 - you out there?
I should have known better, but a while back I bought a fleabay, cheap-o, pressure regulator diaphragm, and now have somewhat of a cold start problem on my 90. seems I have to crank 3 or 4 seconds without a start. usually, it will start on the second try - sometimes third. I've been recovering from a knee replacement, and finally got around to putting a pressure gauge on the thing. key on, pressure to 42 psi, after a couple seconds, a drop to 40 -- so far, so good, but it continues to drop. after 10-12 seconds, a drop to 20 psi, and it continues to around 10 psi after 32-34 seconds. at idle, I'm holding about 38 psi, and with revving the engine slightly, it fluctuates between 38-40 psi. upon shutting the engine down, a drop to 20 psi after 7 or 8 seconds, and 10 psi after 30 seconds. the injectors are new (well, rebuilds) boschIII's from FIC, so I'm fairly sure it not a leaking injector issue. I pulled the vacuum line off the FPR, and there was no signs of leaking fuel. I need to run out today to get a couple (fuel line) clamps for further testing, but my gut feeling, it's the FPR diaphragm. I did not have any starting issues prior to installing the diaphragm and injectors. the car seems to run fine otherwise. hot/warm starts - perfect. there was an older thread about defective FP diaphragms, and I'm thinking my problem may be related. what has me stumped, is when I hit the key, and the engine is cranking within those first two seconds, the rails are pressurized at 40-42 psi, oil pressure should be high enough for the start sequence. seems to me, it should start - ??? based on my initial fuel pressure readings, any comments?
WVZR-1 - you out there?
Last edited by Joe C; 08-11-2014 at 06:49 AM.
08-11-2014, 07:17 AM
#3
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Thread Starter
08-11-2014, 07:44 AM
#4
Melting Slicks
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Joe, read my thread regarding this same issue...you may find it a very interesting read---> New Fuel Regulator Diaphragm DEFECT Alert!
A defective FPR diaphragm can absolutely cause hard starts...
A defective FPR diaphragm can absolutely cause hard starts...
08-11-2014, 07:53 AM
#5
Instructor
FP regulators can fail in two ways...the diaphragm can rupture allowing fuel into the vacuum line and then into the intake manifold...you have checked this and it seems Ok
the other is the valve and spring assembly that is supposed to maintain a fuel pressure...I suspect that the valve is not seating properly allowing the fuel pressure to quickly drop off
The FP in my 90 does not drop off that fast.
the other is the valve and spring assembly that is supposed to maintain a fuel pressure...I suspect that the valve is not seating properly allowing the fuel pressure to quickly drop off
The FP in my 90 does not drop off that fast.
08-11-2014, 07:59 AM
#6
Race Director
Thread Starter
Joe, read my thread regarding this same issue...you may find it a very interesting read---> New Fuel Regulator Diaphragm DEFECT Alert!
A defective FPR diaphragm can absolutely cause hard starts...
A defective FPR diaphragm can absolutely cause hard starts...
- been there - originally, I posted this on you're subject thread. BTW, good info on your original thread!
08-11-2014, 10:45 AM
#7
Drifting
I posted this on an older thread, but since I wasn't getting any response, I deleted that post, and thought I'd start a new thread.
I should have known better, but a while back I bought a fleabay, cheap-o, pressure regulator diaphragm, and now have somewhat of a cold start problem on my 90. seems I have to crank 3 or 4 seconds without a start. usually, it will start on the second try - sometimes third. I've been recovering from a knee replacement, and finally got around to putting a pressure gauge on the thing. key on, pressure to 42 psi, after a couple seconds, a drop to 40 -- so far, so good, but it continues to drop. after 10-12 seconds, a drop to 20 psi, and it continues to around 10 psi after 32-34 seconds. at idle, I'm holding about 38 psi, and with revving the engine slightly, it fluctuates between 38-40 psi. upon shutting the engine down, a drop to 20 psi after 7 or 8 seconds, and 10 psi after 30 seconds. the injectors are new (well, rebuilds) boschIII's from FIC, so I'm fairly sure it not a leaking injector issue. I pulled the vacuum line off the FPR, and there was no signs of leaking fuel. I need to run out today to get a couple (fuel line) clamps for further testing, but my gut feeling, it's the FPR diaphragm. I did not have any starting issues prior to installing the diaphragm and injectors. the car seems to run fine otherwise. hot/warm starts - perfect. there was an older thread about defective FP diaphragms, and I'm thinking my problem may be related. what has me stumped, is when I hit the key, and the engine is cranking within those first two seconds, the rails are pressurized at 40-42 psi, oil pressure should be high enough for the start sequence. seems to me, it should start - ??? based on my initial fuel pressure readings, any comments?
WVZR-1 - you out there?
I should have known better, but a while back I bought a fleabay, cheap-o, pressure regulator diaphragm, and now have somewhat of a cold start problem on my 90. seems I have to crank 3 or 4 seconds without a start. usually, it will start on the second try - sometimes third. I've been recovering from a knee replacement, and finally got around to putting a pressure gauge on the thing. key on, pressure to 42 psi, after a couple seconds, a drop to 40 -- so far, so good, but it continues to drop. after 10-12 seconds, a drop to 20 psi, and it continues to around 10 psi after 32-34 seconds. at idle, I'm holding about 38 psi, and with revving the engine slightly, it fluctuates between 38-40 psi. upon shutting the engine down, a drop to 20 psi after 7 or 8 seconds, and 10 psi after 30 seconds. the injectors are new (well, rebuilds) boschIII's from FIC, so I'm fairly sure it not a leaking injector issue. I pulled the vacuum line off the FPR, and there was no signs of leaking fuel. I need to run out today to get a couple (fuel line) clamps for further testing, but my gut feeling, it's the FPR diaphragm. I did not have any starting issues prior to installing the diaphragm and injectors. the car seems to run fine otherwise. hot/warm starts - perfect. there was an older thread about defective FP diaphragms, and I'm thinking my problem may be related. what has me stumped, is when I hit the key, and the engine is cranking within those first two seconds, the rails are pressurized at 40-42 psi, oil pressure should be high enough for the start sequence. seems to me, it should start - ??? based on my initial fuel pressure readings, any comments?
WVZR-1 - you out there?
Just FYI, I saw this and not sure you'll be having the same problem, but since you do have a 90 as I do, and you're dealing with fuel pressure drop issues, one member here brought it to my attention on another of my posts that it also could be the pulsator on your fuel pump line inside the gas door. If you changed it out already, or bridged a gap with some fuel hose then doubtful, but that little bastard can cause a lot of misdiagnosed problems with the fuel pressure from what I can tell if its loose or just old and worn out like mine looks. If you haven't dealt with it, I'd pull out the pump assembly and check it to see if it's leaking down the sides/wobbly etc, because that part of the system should be high pressure I believe.
08-11-2014, 12:17 PM
#8
Race Director
Thread Starter
Just FYI, I saw this and not sure you'll be having the same problem, but since you do have a 90 as I do, and you're dealing with fuel pressure drop issues, one member here brought it to my attention on another of my posts that it also could be the pulsator on your fuel pump line inside the gas door. If you changed it out already, or bridged a gap with some fuel hose then doubtful, but that little bastard can cause a lot of misdiagnosed problems with the fuel pressure from what I can tell if its loose or just old and worn out like mine looks. If you haven't dealt with it, I'd pull out the pump assembly and check it to see if it's leaking down the sides/wobbly etc, because that part of the system should be high pressure I believe.
08-11-2014, 01:47 PM
#9
Safety Car
I posted this on an older thread, but since I wasn't getting any response, I deleted that post, and thought I'd start a new thread.
I should have known better, but a while back I bought a fleabay, cheap-o, pressure regulator diaphragm, and now have somewhat of a cold start problem on my 90. seems I have to crank 3 or 4 seconds without a start. usually, it will start on the second try - sometimes third. I've been recovering from a knee replacement, and finally got around to putting a pressure gauge on the thing. key on, pressure to 42 psi, after a couple seconds, a drop to 40 -- so far, so good, but it continues to drop. after 10-12 seconds, a drop to 20 psi, and it continues to around 10 psi after 32-34 seconds. at idle, I'm holding about 38 psi, and with revving the engine slightly, it fluctuates between 38-40 psi. upon shutting the engine down, a drop to 20 psi after 7 or 8 seconds, and 10 psi after 30 seconds. the injectors are new (well, rebuilds) boschIII's from FIC, so I'm fairly sure it not a leaking injector issue. I pulled the vacuum line off the FPR, and there was no signs of leaking fuel. I need to run out today to get a couple (fuel line) clamps for further testing, but my gut feeling, it's the FPR diaphragm. I did not have any starting issues prior to installing the diaphragm and injectors. the car seems to run fine otherwise. hot/warm starts - perfect. there was an older thread about defective FP diaphragms, and I'm thinking my problem may be related. what has me stumped, is when I hit the key, and the engine is cranking within those first two seconds, the rails are pressurized at 40-42 psi, oil pressure should be high enough for the start sequence. seems to me, it should start - ??? based on my initial fuel pressure readings, any comments?
WVZR-1 - you out there?
I should have known better, but a while back I bought a fleabay, cheap-o, pressure regulator diaphragm, and now have somewhat of a cold start problem on my 90. seems I have to crank 3 or 4 seconds without a start. usually, it will start on the second try - sometimes third. I've been recovering from a knee replacement, and finally got around to putting a pressure gauge on the thing. key on, pressure to 42 psi, after a couple seconds, a drop to 40 -- so far, so good, but it continues to drop. after 10-12 seconds, a drop to 20 psi, and it continues to around 10 psi after 32-34 seconds. at idle, I'm holding about 38 psi, and with revving the engine slightly, it fluctuates between 38-40 psi. upon shutting the engine down, a drop to 20 psi after 7 or 8 seconds, and 10 psi after 30 seconds. the injectors are new (well, rebuilds) boschIII's from FIC, so I'm fairly sure it not a leaking injector issue. I pulled the vacuum line off the FPR, and there was no signs of leaking fuel. I need to run out today to get a couple (fuel line) clamps for further testing, but my gut feeling, it's the FPR diaphragm. I did not have any starting issues prior to installing the diaphragm and injectors. the car seems to run fine otherwise. hot/warm starts - perfect. there was an older thread about defective FP diaphragms, and I'm thinking my problem may be related. what has me stumped, is when I hit the key, and the engine is cranking within those first two seconds, the rails are pressurized at 40-42 psi, oil pressure should be high enough for the start sequence. seems to me, it should start - ??? based on my initial fuel pressure readings, any comments?
WVZR-1 - you out there?
I suspect the problem is not with the fuel pressure regulator, as noted during the cranking sequence the fuel pressure is at 42 PSI, which is fine. More then likely the injectors are supplying a different amount of fuel at cranking then the original injectors were. The tune probably needs to be adjusted.
08-11-2014, 05:50 PM
#11
Race Director
Thread Starter
I suspect the problem is not with the fuel pressure regulator, as noted during the cranking sequence the fuel pressure is at 42 PSI, which is fine. More then likely the injectors are supplying a different amount of fuel at cranking then the original injectors were. The tune probably needs to be adjusted.
w/ the tuning thing, but still think there's another fuel system component issue here. there's no way I can do my own re-tune, so somewhere down the road, and after I stabilize the fuel pressure thing, I need to find a tuner in the Daytona area.