Starts running and quits...
Thread Starter
7th Gear
Joined: Mar 2006
Posts: 7
Likes: 0
Starts running and quits...
I have an '85 vette I just purchased, it has been sitting up for 10 years. I installed a new fuel pump, filter, strainer, cleaned the injectors and all it will do is crank and run for a few seconds and quit. I've done everything I know to do. I was wanting to see if anyone else had ran into this problem. This is the first vette I have owned. Thanks
Melting Slicks
Joined: Jan 2005
Posts: 2,658
Likes: 4
From: Clifton Park NY
Check to make sure the fuel pump turns on when you first turn the key on. May be a relay too. I just ran into this problem myself and it ended up being the wire on the relay came off a bit.
Thread Starter
7th Gear
Joined: Mar 2006
Posts: 7
Likes: 0
relay turns on and pumps up, that is the only time it runs for a few seconds, after the fuel pump cycles and pumps up, its like it is not keeping the right amount of fuel pressure or something is cutting off the injectors
Le Mans Master
Joined: Apr 2000
Posts: 6,341
Likes: 1
From: Shelton CT
Unplug the MAF sensor.. Even though it will give an SES light, the car should run in home limp mode with it unplugged. When Mine died, it kept starting and stalling like yours, I unplugged the MAF and drove home over 120miles. Ran rich, but was fine.. Replaced it with a GM MAF (don't do the aftermarket CRAP fro mautozone/pepboys, etc.. as they don't work (I tried 2 before giving up)).
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Have you checked for trouble codes? You WILL eventually need a factory service manual to help you read, understand, and trouble shoot codes. The sooner you get one, the more money it can save you. I agree with checking out the fuel pressure, when, how, and for how long, while you are waiting for the FSM to show up.
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Burning Brakes
Joined: Dec 1999
Posts: 765
Likes: 11
Cruise-In I Veteran
Before you yank that pump out again, check these things out first.
I assume that the pump cycles to prime the system, but does the pressure hold if you don't crank the engine and leave the key on? If the pressure drops off quick, then your pressure regulator should be looked at.
BTW what is the pressure?
If the pressure holds, then crank the motor up and watch the pressure. If the pressure drops as you crank, its in the fuel pump circuit, but may not be the pump itself.
The oil pressure sending unit is supposed to keep the pump running while the engine is running. With the key on, short the oil pressure sending unit to see if the fuel pump relay clicks on. Click with no fuel pressure means you are going to have to yank the pump out again.
Good luck and keep us posted
I assume that the pump cycles to prime the system, but does the pressure hold if you don't crank the engine and leave the key on? If the pressure drops off quick, then your pressure regulator should be looked at.
BTW what is the pressure?
If the pressure holds, then crank the motor up and watch the pressure. If the pressure drops as you crank, its in the fuel pump circuit, but may not be the pump itself.
The oil pressure sending unit is supposed to keep the pump running while the engine is running. With the key on, short the oil pressure sending unit to see if the fuel pump relay clicks on. Click with no fuel pressure means you are going to have to yank the pump out again.
Good luck and keep us posted
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Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Well, I suppose it could be a bad fuel pump-but I'm thinking bad injector(s) get that pressure guage-and if the pump is pumping up the pressure
and it drops quickly-you probably have a bad injector(s) leaky.
and it drops quickly-you probably have a bad injector(s) leaky.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
The tests lowflyer suggests are a good idea. The comment that it "may not be the pump itself is definitely true. He has proved the pump works. Otherwise, there are some incorrect statements at the end of his post.
The oil pressure sending unit does nothing more than send the signal to the IP gauge for the oil pressure reading. Next to, and in some early models, integral with, the sending unit, there is an oil pressure switch. Once oil pressure reaches ~4 psi, the switch closes and sends power directly to the fuel pump. The oil pressure switch does NOT send power to the fuel pump relay, so no click at the relay means nothing, if and when you might "short the oil pressure sending unit". The power to the fuel pump, directed by the oil pressure switch, is a back up to the primary source of power, the fuel pump relay as triggered by the ECM. Besides the initial 2 second priming period, the ECM powers the relay, when it senses pulses from the HEI, indicating that the engine is turning. It continues to activate the fuel pump relay as long as those pulses are present. In short, the fuel pump relay is supposed to power the fuel pump during cranking AND running.
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Originally Posted by lowflyer
The oil pressure sending unit is supposed to keep the pump running while the engine is running. With the key on, short the oil pressure sending unit to see if the fuel pump relay clicks on.
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Thread Starter
7th Gear
Joined: Mar 2006
Posts: 7
Likes: 0
What keeps the injectors on?
After the engine supposedly starts, which in my case it isn't, could something be cutting the injectors off? If I bypass the power to the pump and keep it on with the pressure up, it still won't run.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
My comments above were mostly to undo the harm lowflyers mis-information may have caused. I have no doubt that your pump runs. You said it built up pressure during the 2 second priming period. That proves that it works and whether it is the right pump or not, that doesn't cut off the power while cranking or when it should be starting. I'm not convinced that you have done a complete diagnosis on when and how much fuel pressure there is. Otherwise you wouldn't have asked about the injectors being turned off. I have no idea how you are "bypass the power to the pump" or why you think you have to. Have you checked out the output from the ECM and the oil pressure switch? Are those systems working properly?
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Instructor
Joined: Oct 2005
Posts: 108
Likes: 0
From: Acton, MA 1990 ZF6 Coupe, Z51
Reread CFI's post....A bad oil pressure switch will not cause your problem...When the key is turned on, the ECM runs the Fuel pump relay(which runs the pump) for a two second priming period, then shuts off..When the engine is then cranked, the ECM needs feedback pulses from the HEI distributor to run the fuel pump relay....
Do you have a noid light?? If so, connect it across a fuel injector plug, bet you will see no 12v while the engine is cranking, this indicates the ECM is not receiving feedback pulses...
Get a service manual to trace out the wiring to the ECM from the distributor, it should also have tests to detirmine if the pulse module is bad....
Do you have a noid light?? If so, connect it across a fuel injector plug, bet you will see no 12v while the engine is cranking, this indicates the ECM is not receiving feedback pulses...
Get a service manual to trace out the wiring to the ECM from the distributor, it should also have tests to detirmine if the pulse module is bad....
Burning Brakes
Joined: Nov 2005
Posts: 848
Likes: 1
From: 1992 LT1 6 speed Cayman Islands
Originally Posted by geezel
Probably a really stupid remark, but are you using the original ignition key (with the code pellet in it)? A copy of the key without the pellet will cause the 2-3 second run condition.
Herris
Instructor
Joined: Oct 2005
Posts: 108
Likes: 0
From: Acton, MA 1990 ZF6 Coupe, Z51
Originally Posted by geezel
Probably a really stupid remark, but are you using the original ignition key (with the code pellet in it)? A copy of the key without the pellet will cause the 2-3 second run condition.
No VATS in 1985.....
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by JeffM1243
Do you have a noid light?? If so, connect it across a fuel injector plug, bet you will see no 12v while the engine is cranking, this indicates the ECM is not receiving feedback pulses...
Originally Posted by JeffM1243
Get a service manual to trace out the wiring to the ECM from the distributor, it should also have tests to detirmine if the pulse module is bad....