Mattkovitch

Everytime i start my car from a cold start it cranks wayyy longer than it should, but only at cold starts. when the engine is warm already it starts up right away(almost too fast) and then revs up past 1,000 rpms and then drops and dies. the only way i can get it going when it does this is to start it and quick pull it into gear, then its fine and i can even put it back into park and it will idle like normal. whats up with it? its a 1991 305 with a tbi.

OrangeBird

iTrader: (1)

When you turn the key to the "run" position , do you hear the fuel pump do it's 3 second prime ?

If not , then it's taking till cranking over the engine has built up enough oil pressure to activate the fuel pump switch that monitors the engine's oil pressure for the pump to turn on and supply fuel . Of course when warm , the oil pressure comes up all that much faster , and less cranking is required .

If it is not doing the three second prime , the first thing to check is the fuel pump relay ....

zraffz

Bad check valve?

Mattkovitch

What does the fuel pumps 3 second prime sound like?

OrangeBird

iTrader: (1)

Have the driver's door opened , and without actually starting the engine , put the key to the "ON" position and listen for a "whirring" sound that comes from the rear of the car for 3 seconds . If need be , have someone else put the key to "ON" while you have your ear a foot or two away from the gas cap with the gas cap door opened . There is no pump quiet enough that you won't be able to hear it prime as long as it's functioning .

If you don't hear that sound , start by troubleshooting the fuel pump relay ...

TheJoeY88

iTrader: (2)

Mine is doing the same thing, but i do hear the fuel pump prime when i turn it to the on position

novaderrik

a weak regulator will cause it to take longer to build up fuel pressure. a test for this is to prime it a few times by turning the key on until the pump shuts off, then turning the key off, then on again, then off, then trying to start it. there is also a check valve in the pump itself that can go bad, which allows pressure to bleed back into the tank after you shut the key off.

Mattkovitch

Okay, I'll try that. Any ideas why it would die it dies when I start it already hot? It's annoying and I'd like to get it fixed

OrangeBird

iTrader: (1)

Matt , and Joe , Here's the deal ;

There are quite a number of things that could cause an engine to need excessive cranking time to start . One of the more common ones is the lack of the 3 second prime as I mentioned earlier and zraff's check valve and novaderrik's regulator are also prime candidates as well . So to are the spark plugs , distributor cap & rotor , and all the other "deferred maintenance" items (as Sofa so aptly calls them) . Basically speaking , to try to post up a list of every part that could cause excessive cranking would amount to posting up a list of just about every part of both the fuel and engine electrical systems , a tall order indeed .

ploegi

So post the most common failure. The pump relay. All else being equal, it's a typical culprit.

OrangeBird

iTrader: (1)

Last sentence , post #2 ......

ASE doc

It is interesting that the OP's engine will remain running if he places a load on it right away.

The points that OrangeBird brought up can't be overstated. Engine tune is very critical on engine start when, even if the engine is warm, the combustion chambers are cooled down from normal running temp on start up. The need for sufficient spark energy and plug gap condition is even more critical on a cold start.

Another issue that could cause the OP's particular effect is the IAC or minimum idle air setting. Even if the setting hasn't been altered during a tune up, worn throttle shaft bores can cause the setting to change. You may want to check the throttle shaft for runout and also check the IAC for carbon build up and sticking. One clue to worn throttle shaft bushings is TPS minimum voltage. I use my scan tool and watch TPS voltage while slightly opening and closing the throttle several times. It should always return to the same value. If it doesn't, that likely means the shaft bores are worn. You can check for runout by feeling and watching for lateral movement.

I have been able to cover slightly worn bores by raising minimum idle air just a little. The 91 will allow for a change in minimum TPS as this is an adaptive in that ECM. Just don't go over 1 volt minimum. I try to stay below .9 volts to be safe.