Appreciate the recommendation.
Fuel Issue ? - 95 Stock LT1
Thread Starter
Pro
Joined: Jan 2015
Posts: 538
Likes: 36
From: Northern Colorado
Fuel Issue ? - 95 Stock LT1
Couple of recent issues that I figure are related; either regulator, pump or maybe something cheap like the fuel filter. I will be grabbing a loaner fuel system pressure tester later today and getting to work. Wanted to toss this out there looking for other areas of concern or discussion.
1. Slow start. Prior it would start quickly upon cranking, almost immediate. Now takes 5-10 seconds or even a couple of cycles.
2. Hesitation under acceleration. Seems to be a hesitation, not a 'stutter' type hesitation but a 'smooth hesitation' when accelerating. Hard to explain.
3. Last week parked on a slight downward incline; started for about 10 seconds and ran very rough, then died and a strong smell of fuel. Upon restart it smoothed out and got me home.
Thank you for any direction. Best regards, -Steve
1. Slow start. Prior it would start quickly upon cranking, almost immediate. Now takes 5-10 seconds or even a couple of cycles.
2. Hesitation under acceleration. Seems to be a hesitation, not a 'stutter' type hesitation but a 'smooth hesitation' when accelerating. Hard to explain.
3. Last week parked on a slight downward incline; started for about 10 seconds and ran very rough, then died and a strong smell of fuel. Upon restart it smoothed out and got me home.
Thank you for any direction. Best regards, -Steve
Le Mans Master
Joined: Oct 2004
Posts: 7,706
Likes: 485
From: Everett WA
C4 of Year Finalist (appearance mods) 2019
You're on the right track. Need to tape the fuel pressure gauge to the outside of the windshield so that you can see the FP when the motor is hesitating. The LT1 needs approx 40-42 lbs not only to start but to keep the engine running at high rpm.
The fuel filter & pump are likely needing replacement. Also if/when replacing the fuel pump also replace the two relays that interact with the pump. (I believe that the 95 has two relays).
The fuel filter & pump are likely needing replacement. Also if/when replacing the fuel pump also replace the two relays that interact with the pump. (I believe that the 95 has two relays).
Thread Starter
Pro
Joined: Jan 2015
Posts: 538
Likes: 36
From: Northern Colorado
You're on the right track. Need to tape the fuel pressure gauge to the outside of the windshield so that you can see the FP when the motor is hesitating. The LT1 needs approx 40-42 lbs not only to start but to keep the engine running at high rpm.
The fuel filter & pump are likely needing replacement. Also if/when replacing the fuel pump also replace the two relays that interact with the pump. (I believe that the 95 has two relays).
The fuel filter & pump are likely needing replacement. Also if/when replacing the fuel pump also replace the two relays that interact with the pump. (I believe that the 95 has two relays).
Thank you for the reply. On the way home I rented a pressure gauge, nice and easy. Key on, starts at 44. Less then five minutes and below 30. Looks like a new fuel pump/relays will be ordered.
Thread Starter
Pro
Joined: Jan 2015
Posts: 538
Likes: 36
From: Northern Colorado
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
The slow start actually points to a potential problem with the fuel pump relay. I noticed this while playing with the CCM; if you disable the fuel pump relay and try to start the car, it will take a few seconds to fire because the fuel pump is only energized by the oil pressure switch exceeding 4 PSI of oil pressure. Once I turned the relay back on it was back to instant starts.
So worth checking to make sure that it's functioning. If it isn't, then the only thing keeping your fuel pump running is the oil pressure switch (which is also connected directly to the "Check Gauges" light on your dash).
So worth checking to make sure that it's functioning. If it isn't, then the only thing keeping your fuel pump running is the oil pressure switch (which is also connected directly to the "Check Gauges" light on your dash).
Thread Starter
Pro
Joined: Jan 2015
Posts: 538
Likes: 36
From: Northern Colorado
The slow start actually points to a potential problem with the fuel pump relay. I noticed this while playing with the CCM; if you disable the fuel pump relay and try to start the car, it will take a few seconds to fire because the fuel pump is only energized by the oil pressure switch exceeding 4 PSI of oil pressure. Once I turned the relay back on it was back to instant starts.
So worth checking to make sure that it's functioning. If it isn't, then the only thing keeping your fuel pump running is the oil pressure switch (which is also connected directly to the "Check Gauges" light on your dash).
So worth checking to make sure that it's functioning. If it isn't, then the only thing keeping your fuel pump running is the oil pressure switch (which is also connected directly to the "Check Gauges" light on your dash).
Thank you Nomake. Would a relay also cause the hesitation when under load?? Either way, it is looking like I need to grab a couple of relays as you and Mr Peabody have recommended. I was able to complete a pressure test; key-on about 42, idle at 38. WOT and remove the vacuum line from regulator and hits about 46+ Leakdown, less than two minutes 42 down to 36 and below 30 after about five minutes.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
The relay failing would only cause hesitation under load if you're also encountering a condition that's causing the oil pressure switch to see less than 4 PSI of oil pressure at the same time (because, were this to happen, power to the fuel pump would be cut off since the relay was no longer working to keep it on).
From your leakdown test, you have a massive leak somewhere. Either a stuck injector is leaking fuel into the cylinders, or your regulator is leaking fuel into a vacuum port, or your regulator is stuck and is leaking fuel into the return.
From your leakdown test, you have a massive leak somewhere. Either a stuck injector is leaking fuel into the cylinders, or your regulator is leaking fuel into a vacuum port, or your regulator is stuck and is leaking fuel into the return.
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