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I have an issue starting the car, sometimes it fires right up, other times it takes some cranking. I get 40psi when I turn the key on, and it fired right up, stayed at 40psi while idling, taped the gauge to the windshield and when under power it’s right around 38-40 but when I let off the throttle and stop it’s around 34psi. When I shut it off it stays at 40psi for awhile and there’s no smell of gas from the regulator. Wondering if the pump is getting weak ? This car sat for 12 years until a few months ago.
Thanks for the helpful post. The fuel pressure will dip to 34psi when deacceleratiing and at a stop. The crank no start will happen even with a warmed up engine, it will crank and act like a carbureted engine and you have to press the throttle pedal a few times for it to fire. It doesn’t always happen, and the day I tested my FP it didn’t hesitate and it fired right up. Could this still be a CSI issue even with a warm engine ? Thanks for the help.
Thanks for the update, I thought the idle pressure seemed low. I ordered a new pump, stainer and pulsator and gasket. Like you mentioned, it's been sitting a while and new pumps are pretty cheap. Going to install it next week will let you know what I find.
I do not think the pressure is low, first run the engine with the vacuum hose off at the regulator and see what the pressure is? Also how accurate is your gauge? Need to verify your gauge against a known pressure to make sure it is ok.
I do not think the pressure is low, first run the engine with the vacuum hose off at the regulator and see what the pressure is? Also how accurate is your gauge? Need to verify your gauge against a known pressure to make sure it is ok.
I understand that the gauge may or may not be accurate, but I think it’s okay. With key on engine off, it jumps right to 40, and when starting will move a bit +/- at idle but stay at 40ish. Its when I drive the gauge seems to move a lot between 30 and 40 and when coasting with the clutch in and foot off the throttle the gauge drops to between 30-35 for a while, then will climb back to 40. My biggest issue diagnosing the hard start issue is when I use the gauge to test it, the car fires right up. I can never seem to get the hard start issue to happen when using the gauge. The car sat for 12 years, and I figure for less than $100 I can replace the pump, strainer, pulsator and either get lucky or rule the pump out. I plan on keeping and driving the car for a while, so want to get it all sorted before it becomes my daily.
(I’m also replacing the clutch and flywheel next week to hopefully fix the 3000rpm vibration that you helped me with)
The fuel pressure regulator is pressure refenced so it will drop down to 30 to 35 psi with your foot off the throttle and car coasting with high engine vacuum. The goal of the regulator is to keep the pressure difference between the fuel in the fuel rails and the pressure in the intake manifold at 42 psi. At wot there is no intake manifold vacuum so the fuel pressure will be at 42 psi. Coasting foot off throttle high engine rpm will result in an intake pressure of only 5 psi absolute or 20 inches of vacuum (note 20 inches of vacuum is roughly 10 psi of vacuum). This means the fuel pressure will drop to 32 psi but the pressure differential will still be 42 psi between the rail and the intake manifold.
Last edited by bjankuski; Mar 11, 2024 at 05:32 PM.
I do not think the pressure is low, first run the engine with the vacuum hose off at the regulator and see what the pressure is?
Replaced the fuel pump today and I haven’t had the hard start issue so far. Key On Engine Off pressure is at 42, Engine Running pressure is 35 at idle, blip throttle and pressure rises to 44, remove the vacuum line at regulator at idle and it jumps to 47. Replace vacuum line and the pressure drops back to 35 at idle. Also now when I have Key On Engine Off the pressure jumps to 44 then I hear a click and it drops to 42, never seen or heard that before. So it seems to me the regulator is working like it should ?
EDIT: The hard start happened, let the car sit and left the gauge hooked up, it bled down to 33, turned key on, jumped to 44 then heard the click then dropped to 42, when I when to start it cranked for about 5 seconds then slowly caught and fired up and the pressure didn’t drop.
Sounds like your hard start is not a pressure issue then. I’d want to see data like iats, ect, and such. The timing is referenced off those, and I can’t remember if that model year had a cold start fuel injector. If it does, that could be acting up. I’m leaning more along the lines of timing or fuel volume being the issue. Have you put a vacuum gauge on it while it is running good?
Sounds like your hard start is not a pressure issue then. I’d want to see data like iats, ect, and such. The timing is referenced off those, and I can’t remember if that model year had a cold start fuel injector. If it does, that could be acting up. I’m leaning more along the lines of timing or fuel volume being the issue. Have you put a vacuum gauge on it while it is running good?
I fixed the issue, it was leaky fuel injectors. I replaced them with Bosch 3s and now it fires right up. One more thing crossed off the list.
Weak Fuel Pump ?
