Fuel pressure details
dpollard
06-24-2006, 12:56 PM
Hey guys- I'm in process of diagnosing a hard starting issue. Many thanks to all the good information contained. I believe I am experiencing a fuel pressure drop and could use a few details.
Fast rundown -
vehicle is a 95 jimmy 4x4 4.3 W code. Hard starting occurs primarily when the engine is cooling down. While the engine is still hot -starts fine; after it sits overnight - starts okay (sometimes 2-3 trys); but if it sits after an hour or so, it takes 4-6 cranks to get it going. No other driveability issues have come up. Have gone through general tune up, battery issues. (Pump and CPI was replaced a few years back, but that doesn't mean much)
Fuel pressure key on engine off jumps to 62 (tested at shrader valve). as the pump shuts off, it immediately drops to 58ish. after 5 secs its 54, after 15 sec 50, after 1 minute around 40. Judging by what I've read here, I have a leak (small?). Before tearing off the plenum, etc. What is considered a "normal" bleed down rate? And, what tests can I perform to isolate the leak?
As an aside, I am a bit puzzled why the problem is most evident during cooldown? Any explanations welcome.
Thanks in advance-
Dave
Fast rundown -
vehicle is a 95 jimmy 4x4 4.3 W code. Hard starting occurs primarily when the engine is cooling down. While the engine is still hot -starts fine; after it sits overnight - starts okay (sometimes 2-3 trys); but if it sits after an hour or so, it takes 4-6 cranks to get it going. No other driveability issues have come up. Have gone through general tune up, battery issues. (Pump and CPI was replaced a few years back, but that doesn't mean much)
Fuel pressure key on engine off jumps to 62 (tested at shrader valve). as the pump shuts off, it immediately drops to 58ish. after 5 secs its 54, after 15 sec 50, after 1 minute around 40. Judging by what I've read here, I have a leak (small?). Before tearing off the plenum, etc. What is considered a "normal" bleed down rate? And, what tests can I perform to isolate the leak?
As an aside, I am a bit puzzled why the problem is most evident during cooldown? Any explanations welcome.
Thanks in advance-
Dave
rlith
06-26-2006, 09:24 AM
Hey guys- I'm in process of diagnosing a hard starting issue. Many thanks to all the good information contained. I believe I am experiencing a fuel pressure drop and could use a few details.
Fast rundown -
vehicle is a 95 jimmy 4x4 4.3 W code. Hard starting occurs primarily when the engine is cooling down. While the engine is still hot -starts fine; after it sits overnight - starts okay (sometimes 2-3 trys); but if it sits after an hour or so, it takes 4-6 cranks to get it going. No other driveability issues have come up. Have gone through general tune up, battery issues. (Pump and CPI was replaced a few years back, but that doesn't mean much)
Fuel pressure key on engine off jumps to 62 (tested at shrader valve). as the pump shuts off, it immediately drops to 58ish. after 5 secs its 54, after 15 sec 50, after 1 minute around 40. Judging by what I've read here, I have a leak (small?). Before tearing off the plenum, etc. What is considered a "normal" bleed down rate? And, what tests can I perform to isolate the leak?
As an aside, I am a bit puzzled why the problem is most evident during cooldown? Any explanations welcome.
Thanks in advance-
Dave
Bleed down is way too fast.... Sounds like a leaking regulator...
Fast rundown -
vehicle is a 95 jimmy 4x4 4.3 W code. Hard starting occurs primarily when the engine is cooling down. While the engine is still hot -starts fine; after it sits overnight - starts okay (sometimes 2-3 trys); but if it sits after an hour or so, it takes 4-6 cranks to get it going. No other driveability issues have come up. Have gone through general tune up, battery issues. (Pump and CPI was replaced a few years back, but that doesn't mean much)
Fuel pressure key on engine off jumps to 62 (tested at shrader valve). as the pump shuts off, it immediately drops to 58ish. after 5 secs its 54, after 15 sec 50, after 1 minute around 40. Judging by what I've read here, I have a leak (small?). Before tearing off the plenum, etc. What is considered a "normal" bleed down rate? And, what tests can I perform to isolate the leak?
As an aside, I am a bit puzzled why the problem is most evident during cooldown? Any explanations welcome.
Thanks in advance-
Dave
Bleed down is way too fast.... Sounds like a leaking regulator...
wb8yjf
06-26-2006, 10:17 AM
Or maybe the nut kit or regulator?
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