95 Tahoe 4x4, ~5 sec of cranking before starting

[MotoCARR]

1995 Tahoe 4x4, ~205k.

Issue: The truck has to crank for about five seconds before it starts up. Once it starts and is running, motor drives fine. If I drive a bit, park for 5 min or so, and then try to start, it fires up like any other car. The longer it sits after driving the longer it takes to restart, but it never takes longer than about five seconds which can be seen in the video.

The air cleaner has been taken off and we watched the fuel injectors spray while the truck is running and it looks as if plenty of fuel is being sprayed, and I get about 12 mpg city driving which seems to be about normal. One thing to note is that the tubing that goes from the round aircleaner on top of the throttle body to the fender to help bring in air is missing, if that's even an issue worth mentioning.

Thoughts on what the issue could be?
https://www.youtube.com/watch?v=UBTSXvPji1A&feature=player_embedded

 

[MotoCARR]

Doesn't matter if it's 40 deg or 15 deg., or if I have been driving it everyday or for the first time in a week. Same issue.

 

[MO Viet Vet]

Sounds like fuel pressure is bleeding off when shut down long enough. Will have to plumb a fuel pressure gauge in the system and see what pressure you have after sitting for awhile. Likely none when you first open up the system if it is the problem I think you have. Get the reading when you turn key on but do not start the engine, then crank the engine and see what the pressure does, monitor the pressure while at idle and when rev the engine and then shut off and see how long it takes for the pressure to drop. When it bleeds down to almost nothing I bet you can duplicate to problem of 5 second crank before starting. Will need a fuel pump and do the filter while you are at it unless it is relatively new.

 

[MotoCARR]

Thanks for the info., will definitely look into doing that. Should there always be some pressure in the system even with the truck off or is there a rate in which pressure should build? While doing an oil change I was giving the underside a once over and from the looks of things it seems like a new fuel filter has been installed somewhat recently.

 

[MO Viet Vet]

The filter is cheap enough that if you don't know the age and if you do a fuel pump then you should replace it. The system should hold the pressure to within 5 psi of shut down pressure.

 

[MotoCARR]

Thanks, gives me a good starting point to go off of.

 

[MO Viet Vet]

Main thing is monitor those fuel pressure readings before just putting in a new fuel pump. Not an easy job and not the cheapest either. If you had the newer system it is as easy as threading a gauge on to a fuel rail spout, like a tire valve. Easy Peasy.

 

[lesterl]

Try cycling the key a few times on / off to prime the fuel system on a cold crank, this will help rule out bleed off.

Hows your battery? If it is getting a little weak or the starter a little slow you could have extended crank. Timing off could slow it down.

 

[MotoCARR]

Battery is good, only a year old. Perfect day to try cycling the key, it's a balmy 9 deg out today

 

[adam74]

I have the same problem with my 95. sits for a couple days it takes a lil cranking to get it started. new battery, new fuel pump, tune up (plugs,wires,cap and rotor) numerous other stuff under the hood. cap n rotor not ac delco but pretty much everything else is

 

[lesterl]

Try this: When engine is cold (prone to extended cranking), take breather off and spray some carb cleaner into the intake, immedietley crank, if it fires right up we know if we are dealing with an underfueling issue when really cold. If it cranks longer (then we can suspect perhaps we have an over fueling issue.

When is the last time you had the intake cleaned? If there is alot of carbon buildup, the carbon could be absorbing fuel causing delayed start I suppose since it is a wet intake.

 

[adam74]

can you seafoam the intake through the brake booster vacuum line like other vehicles? Ive done that to a few foriegn cars with very good results as far as cleaning them out

 

[lesterl]

Yes you can, make shure the engine is fully warmed up when you do it....

 

[MotoCARR]

Thanks for the info lesterl, I will definitely give the carb cleaner test a shot.

Also wanted to add something I noticed over the weekend.....

Ran into a store for about 15-20 minutes and when I went to start it, I gave it some gas this time to get it going. Truck started within a "normal" amount of crank time, RPMs went up to about 1500 but then immediately started falling down to 0 and the truck died WHILE I was pumping the gas. Tried to start the truck again(not giving it gas) and boom it started and stayed running like a "normal" Tahoe(.5-1sec of cranking).

Is there some sort of temperature sensor that dictates what amount or fuel pressure to use at a particular degree? I have been doing some general fuel system reading and as mentioned it seems like there needs to be more fuel pressure at startup/cold vs running/warm. Rather than it being a fuel pressure issue, could it be a sensor not reading temperature correctly that would tell the computer at what fuel pressue it needs to spray at?

Just thinking out loud

 

[lesterl]

Fuel pressure is FIXED by a regulator.

Fuel quantity is varied by injector pulse-width (longer hold on time more fuel injected).

CTS near the water neck tells the ECM what the engine temp is, and it can manipulate fueling with that.

MAP sensor tells the ECM how hard the engine is working and also affects fueling.

Check for vacum leaks and around the TBI base gasket.

 

[DJ4180]

Had this same problem recently. Turned out to be a crank position sensor that was gummed up. Would start sometimes and shut right off. Wouldn't start other times. No CEL. But mechanic ran scanner and the code came up for bad CPS. Swapped it out. Haven't had the problem since. Maybe look into this?

 

[lesterl]

The 1995 is a TBI engine and I am assuming you have a 1996+ which has the CSFI injection......