cold start valve leaking?
Thread Starter
Pro
Joined: Nov 2005
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From: North Bay Ontario
cold start valve leaking?
'85 coupe
The car is running fine, but I have thought for some time that I had a fuel pressure issue. Finally bought a guage. Turns out I have a fuel pressure problem...
I followed the FSM to diagnose fuel pressure loss symptoms. With the engine cold and ambiant temperature about 10 degrees C - that's about 50 degress F, turn on key, fuel pump runs for 2 secs and reaches 34 lbs but begins to drop off immediately, almost reaching 0 in about 30 secs to a minute. First pinched the fuel supply line - still have same pressure loss then pinched the return line as well - still have same pressure loss. This test eliminates the pulsator, check valve, and fuel pressure regulator as the culprits - leaving only leaking injectors or the cold start valve. (There are no visible external leaks and no smell of raw gas) I recently installed new Bosch III injectors from Jon at FIC last year, and I am pretty sure the new injectors are not the problem, because on other ocassions prior to the new injector install, when relieving pressure in the system there never seemed to be much pressure present.
Everything seems to be pointing to the cold start valve leaking.
The car always starts fine - cold or hot, and doesn't seem to be running rich, no black smoke, no smell - but this alone does not convince me that the cold start valve is not leaking.
Another interesting tidbit...after doing the pinch tests several times to make sure that I was definitely stopping any possible fuel flow in the lines, I started the car. Immediately, upon starting and the car running - the guage dropped to 28 lbs and held steady for about a minute, then jumped back to 34 where it remained constant...which again suggests to me the cold start valve is leaking.
Suggestions?
The car is running fine, but I have thought for some time that I had a fuel pressure issue. Finally bought a guage. Turns out I have a fuel pressure problem...
I followed the FSM to diagnose fuel pressure loss symptoms. With the engine cold and ambiant temperature about 10 degrees C - that's about 50 degress F, turn on key, fuel pump runs for 2 secs and reaches 34 lbs but begins to drop off immediately, almost reaching 0 in about 30 secs to a minute. First pinched the fuel supply line - still have same pressure loss then pinched the return line as well - still have same pressure loss. This test eliminates the pulsator, check valve, and fuel pressure regulator as the culprits - leaving only leaking injectors or the cold start valve. (There are no visible external leaks and no smell of raw gas) I recently installed new Bosch III injectors from Jon at FIC last year, and I am pretty sure the new injectors are not the problem, because on other ocassions prior to the new injector install, when relieving pressure in the system there never seemed to be much pressure present.
Everything seems to be pointing to the cold start valve leaking.
The car always starts fine - cold or hot, and doesn't seem to be running rich, no black smoke, no smell - but this alone does not convince me that the cold start valve is not leaking.
Another interesting tidbit...after doing the pinch tests several times to make sure that I was definitely stopping any possible fuel flow in the lines, I started the car. Immediately, upon starting and the car running - the guage dropped to 28 lbs and held steady for about a minute, then jumped back to 34 where it remained constant...which again suggests to me the cold start valve is leaking.
Suggestions?
Thread Starter
Pro
Joined: Nov 2005
Posts: 602
Likes: 0
From: North Bay Ontario
hmmm...anybody ever followed the diagnostic chart in the FSM to isolate loss of fuel pressure issues??
Seems that a slight variation of the diagnostic process is reveals a different outcome...the FSM says to pressurize the system using the 2 second prime and then to pinch the supply line to isolate fuel pump components and if the leak down continues to pinch the return line to isolate FPR or injectors (assuming you have no other system leaks). I must have followed this procedure a dozen times - always getting the same pressure loss with both lines pinched off. So...I varied from the FSM procedure and pinched the return line BEFORE priming the system for the 2 second interval. Interestingly - the pressure shot up to +60lbs this time and held steady. This eliminated the injectors, the cold start valve and the fuel pump components as the culprits and pointed to the FPR as the problem. As soon as the return line was un-pinched - the fuel pressure began to drop as before. Also, just a note...when the fuel pressure was holding at +60 lbs with the return line pinched, when I pinched the supply line it pushed the pressure up to just around 70 lbs.
Time for a new regulator!
Seems that a slight variation of the diagnostic process is reveals a different outcome...the FSM says to pressurize the system using the 2 second prime and then to pinch the supply line to isolate fuel pump components and if the leak down continues to pinch the return line to isolate FPR or injectors (assuming you have no other system leaks). I must have followed this procedure a dozen times - always getting the same pressure loss with both lines pinched off. So...I varied from the FSM procedure and pinched the return line BEFORE priming the system for the 2 second interval. Interestingly - the pressure shot up to +60lbs this time and held steady. This eliminated the injectors, the cold start valve and the fuel pump components as the culprits and pointed to the FPR as the problem. As soon as the return line was un-pinched - the fuel pressure began to drop as before. Also, just a note...when the fuel pressure was holding at +60 lbs with the return line pinched, when I pinched the supply line it pushed the pressure up to just around 70 lbs.
Time for a new regulator!
