1987 Buick century Hard Starting when cold

[oldsman]

Hi, this venerable 2.8l doesnt want to start when engine is cold, after it warms up it starts fine, otherwise it requires extra cranking after sitting for a few hours. I had a 4.3 GM astro that did that also and it was a temperature sensor.

I know that the computer needs to know how warm the engine is so it can adjust the mix.. does this sound similar?
I know that it isnt a tune up problem as it would occur warm or cold.

As always your help is appreciated.

Thanks.

[way2old]

I think you are on to something with the temperature sensor. You might also want to check fuel pressures just to see if pump is bleeding off overnight.

[oldsman]

Checked starting problem out further, hard to start after bout ten minutes. shop said fuel pump fine coming up to pressure but bleeding down, saying might be regulator, but i dont have a good way to check..any advice? doesnt pump hold up pressure?..though regulator just adjusted i?

[crank.it]

hi oldsman- the pump pushes say 50 pounds to the reg the reg then cuts it to what is needed for the fuel rail.whenn car is off pressure should hold in the fuel rail via regulator for that initial start up then pump is back at 50 pounds their is also the return line that can lose pressure in the line...crank.it

[oldsman]

(08-07-2010 08:32 AM)crank.it Wrote:  hi oldsman- the pump pushes say 50 pounds to the reg the reg then cuts it to what is needed for the fuel rail.whenn car is off pressure should hold in the fuel rail via regulator for that initial start up then pump is back at 50 pounds their is also the return line that can lose pressure in the line...crank.it

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Thanks for the reply Crank.it...sound like its time to pull that intake plenum off and take a look..so if that system is not holding up fuel pressure and bleeding down 8 to 10 psi after 10 minutes and the fuel return is not leaking then my regulator is bad?..i wil make sure that i dont have any bad vacuum lines...by the way i know that there is a vacuum connection with 3 ports on the throttle body and one of them comes off the regulator...any idea which one it is?...thanks

[crank.it]

i think the one on the nipple of the reg (on top)is the vac if that has fuel in it then the diaphram is gone causeing the pressure lo
st ......

[oldsman]

(08-08-2010 08:37 PM)crank.it Wrote:  i think the one on the nipple of the reg (on top)is the vac if that has fuel in it then the diaphram is gone causeing the pressure lo
st ......

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i bought a fuel pressure test gauge and i have a constant 37 pounds pressure while running...what is disturbing is that it appears that i have no fuel pressure at all with the key on with engine not running..i remember reading somewhere about a switch or a relay that will kick in once the computer sees enough oil pressure and allow fuel to get to the engine, engine runs fine once started just hard to start..fuel pressure regulator tucked under the plenum so its hard to check..what does that fuel pump relay do?...i know that i should have pressure at the schrader vale with the key on..Help!

Thanks as always....

[crank.it]

hey oldsman -do you know what pressure its suppose to be???if the pressure is off by ten pounds the computer doesnt allow fuel to the rail or injectors on most cars....when car is running and its at 37 lbs did you rev the engine to see if the fuel was still able to handel the reving engine...or does the eng stumble...or stall....sounds like the pump is losing pressure or a fuel line isleaking pressure????crank.it

[oldsman]

Hey Crank.it...book says 30 lbs or better...car runs fine at all rpms...just no pressure at fuel rail with key on...runs great just hard starting...pump builds pressure while cranking and then it starts...when i turn off key to stop motor then cycle key i can see pressue drop on gauge to nothing at all.... doesnt hold pressure at all...
then duriing cranking it goes up to the 37 lbs then starts 7 to ten seconds after starter turns motor.

[tac]

Many of the older US fuel injected cars had an accident control cutout switch, such that if the engine stopped unexpectedly, it would automoaticall cut off the fuel pump and allow the pressure to drop (back in to the tank if I recall). The idea was that if there was an accident and the ignition was left on, the pump would not continue pushing fuel, in case a line had been broken during the accident.
Perhaps there is something in this circuit that is stuck in this safety mode that is preventing a pre-start pressure buildup?
Sorry not more specific, but it's only the concept that I recall, not the mechanics behind it.

(08-14-2010 11:46 AM)oldsman Wrote:  Hey Crank.it...book says 30 lbs or better...car runs fine at all rpms...just no pressure at fuel rail with key on...runs great just hard starting...pump builds pressure while cranking and then it starts...when i turn off key to stop motor then cycle key i can see pressue drop on gauge to nothing at all.... doesnt hold pressure at all...
then duriing cranking it goes up to the 37 lbs then starts 7 to ten seconds after starter turns motor.

[oldsman]

(08-14-2010 02:21 PM)tac Wrote:  Many of the older US fuel injected cars had an accident control cutout switch, such that if the engine stopped unexpectedly, it would automoaticall cut off the fuel pump and allow the pressure to drop (back in to the tank if I recall). The idea was that if there was an accident and the ignition was left on, the pump would not continue pushing fuel, in case a line had been broken during the accident.
Perhaps there is something in this circuit that is stuck in this safety mode that is preventing a pre-start pressure buildup?
Sorry not more specific, but it's only the concept that I recall, not the mechanics behind it.

(08-14-2010 11:46 AM)oldsman Wrote:  Hey Crank.it...book says 30 lbs or better...car runs fine at all rpms...just no pressure at fuel rail with key on...runs great just hard starting...pump builds pressure while cranking and then it starts...when i turn off key to stop motor then cycle key i can see pressue drop on gauge to nothing at all.... doesnt hold pressure at all...
then duriing cranking it goes up to the 37 lbs then starts 7 to ten seconds after starter turns motor.

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No Tom i dont think that is the problem..just want to narrow it down between fuel pump regulator and fuel pump itself before i get into it...it runs great just has no pressure at all ( cause it drops so fast) between starts. It is either the check valve in the pump not holding pressure or the fuel pump regulator...got to pull plenum to check regulator, and we know what has to be done to get at the fuel pump...i need to know what device is the problem before i tear it down....i believe when everything is proper should see same pump pressure at schrader valve with key on, should be about same with vehicle running...it bleeds down to nothing between starts....

[way2old]

Check the fuel pump relay. The fuel pump should do a 2 second run when the key is turned on.

   

[jgate]

An outlet check valve is incorporated in the discharge outlet to maintain residual or rest pressure when the engine is turned off. This reduces the possibility of vapor-lock and improves starting characteristics. A pressure relief valve is used to prevent over-pressure and potential fuel leakage in the event that pressure or return lines become restricted.

You stated that the pump will build pressure in the start position, install your fuel pressure gauge just after or before the fuel filter, this will take the pressure regulator ,damper, and the rest of the fuel rail components, out of service. If the pressure drops quickly then I would say it is the check valve in the pump. If the pressure holds then the problem could be the pressure regulator,

[crank.it]

hey heres one more a leaking injector will cause bleed down....oooohhh nuts....so no problem starting if you cycle the key rail comes to pressure...you can hear the pump turn on.....iam aiming at leaking injectors....keep us posted oldsman ....crank.it

[oldsman]

Thanks for all the input guys... i do hear the pump energize for 2 seconds when i cycle the key.. tomorrow ill make sure that when i hear the pump come up i check for pressure in the rail again...I know i have to pull the fuel rail to check the injectors... im hoping to find a broken vacuum line at the regulator...strange that it doesnt show any pressure at all with the key on though...by the time i stop motor and turn key back on its all gone...when the pump comes up for 2 seconds i hear it kick out after that like it should...wouldnt the pump keep running if it didnt pressurize the system initially, or does it run for 2 seconds and automatically kick out, pressure or not? Could the regulator be so bad that it will not hold pressure in the rail at all..or is it the check valve in the pump that keep the pressure in the system between starts?....as always thanks for your input...ill start checking parts and quit asking questions....lol

[wrightmercy]

this might be the reason for buick century hard starting, it could be could be as simple as a loose battery wire or as involved as a broken crankshaft! when i got trouble with my car, this is what i did for the buick century repair check the loose battery wiring and check crank sensor.

[afterdsjlrj]

This is great!