Help!!!!! Takes too long to fire
- Thread starter 86SS87GN
- Start date
86SS87GN said:
There are two parts to the ignition module.
One is during low RPM crank, it operates independently of the ecm.
Then as RPM build, the ecm takes control of the timing (still during crank).
*If* the low rpm part of the module fails, then the engine has to crank long enough to hit ~400 rpm for the ecm to take control and start.
There is a normal amount of *long* cranking, in that it can take 2 full engine revolutions for the ignition to synch up. Cold weather can slow it down just enough so that it just seems forever.
If the coolant sensor is misreading then that can be a cause.
Plus your normal, broken wires, poor grounds, etc., etc...
DonnieShort
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- May 27, 2001
Fuel pump relay bad? If so the oil pressure switch is in the mix too, has to see >4psi oil pressure before it will allow relay to energize.
Minor nit, but the oil pressure switch contacts are in parallel with the fuel pump relay contacts. That means it doesn't energize the relay when the oil pressure comes up, it creates a new path for the fuel pump current to flow besides through the relay. Sounds like either the relay, the ecm, or the wiring is bad. Don't forget that if you are triggering a fuel pump hot wire kit off the stock relay (which is how most do it), you have that relay and wiring to check as well.DonnieShort said:
Have you put a fuel pressure gauge on it to see if anything is leaking down? When it starts do you see any black smoke at all? My car was doing the same thing and it turned out to be a injector. The injector/injectors were leaking fuel into the cylinders and then the car would crank for 3-4 seconds until it cleared out and started. With the new injectors it fires right up.
Just a thought
Just a thought
Blown&Injected
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- May 31, 2001
What he said....
I have tried several different 30 amp realys and they all suck. Now I listen carefully after key on to tell if the fuel pump even primed. When it does not, a few taps on the relay fixes it.
Also, what was said earlier - I had a brand new fuel pump had a bad check valve and the fuel pressure prime was lost as fast as it came up - this caused long cranks to start.
I have tried several different 30 amp realys and they all suck. Now I listen carefully after key on to tell if the fuel pump even primed. When it does not, a few taps on the relay fixes it.
Also, what was said earlier - I had a brand new fuel pump had a bad check valve and the fuel pressure prime was lost as fast as it came up - this caused long cranks to start.
rodman99999
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- Mar 25, 2004
Like ijames said: The oil pressure switch doesn't have anything to do with the relay energizing. It's a bypass, in case the relay fails. The fuel pump will work with the oil pressure switch bypassing the relay, but it takes some cranking to build that 4psi. If you unplug the oil pressure switch and jump the terminals in the plug(crude, but effective), and the car starts faster: It's probably the relay.DonnieShort said:
DonnieShort
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- May 27, 2001
rodman99999 said:
I know how it works. I stated it the way I did in sort of laymans terms to help explain, even though "technically" it may not have exact. And if I had money to bet, it is the relay.
My point about the fuel pump check valve has the same leak down effect, but the fuel is returning to the tank past the little check valve in the top of the fuel pump. It then takes a few extra seconds to start because the fuel pump has to play catch up. The initial start pulse of the injectors gives none or very little as the fuel pressure has to be at least 15 psi to really do anything. New more efficient injectors may help, but normaly a good injector cleaning will stop most leakers. I remove the injectors to clean, and inspect the spray pattern. As long as you are cranking the fuel pump will run. A fuel pressure guage will help you find out where in the cranking sequence you achieve enough fuel pressure to start the engine. Later....Danny
DonnieShort
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- May 27, 2001
When you first turn the key on, not to start but on, what happens? Does the fuel pump kick on? Can you hear it? Do you have a fp gauge?
If you turn the key on, the fuel pump will run, you will hear it. Even if it has leaked down it will still run, it just takes a little more time for the system to pressurize. If the fuel pump doesn't run when the key is turned on but after @ 3-4 seconds of cranking you then hear the fuel pump kick on and prime, then it's a bad relay. As I said above, the oil pressure during those 3 seconds of cranking will get high enough for the pressure switch to bypass the relay and allow the pump to run. Which is how I should have worded it to begin with, but it was early and about half asleep so bite me j/k
If you turn the key on, the fuel pump will run, you will hear it. Even if it has leaked down it will still run, it just takes a little more time for the system to pressurize. If the fuel pump doesn't run when the key is turned on but after @ 3-4 seconds of cranking you then hear the fuel pump kick on and prime, then it's a bad relay. As I said above, the oil pressure during those 3 seconds of cranking will get high enough for the pressure switch to bypass the relay and allow the pump to run. Which is how I should have worded it to begin with, but it was early and about half asleep so bite me
j/kI was never trying to say that your diagnosis was incorrect. I was only throwing out another possibility that I didn't explain fully in my first post. Sorry if I made it sound any other way. So is the car fixed? I allways want to hear what it turned out to be. Later....Danny
86SS87GN said:
Assuming the pump kicks on and primes when the key is turned to run as normal and then the fuel pressure drops away enough where you can see the gage pressure decreasing, you have 1 of 3 problems... Pump check valve, regulator, or injectors. Turn the ignition to run and let the pump prime the system. Imediately pinch the fuel supply line with some vise grips. If the pressure now holds its the pump check valve. Repeat for the return line and if pressure holds it's the regulator. If pressure continues to drop under both these tests it's leaky injector(s).
