Help with a hard start issue...

**alchemist1** · 09-01-2009, 02:33 PM

I've got a hard start issue with my 98 Suburban.

It has fuel pressure (good, like 50psi per spec) at the fuel rail and pulling the coil wire at the coil, it is showing spark. But the car takes a long time to start after sitting up for a while. Like 10-12 start cycles (e.g. start for 2-3 seconds, then key off, then start for 2-3 seconds). finally, after a dozen or so cranks, it fires up and runs very well. Never any sign of an issue. Go run errands and it's fine on re-start. But let it sit up overnight or longer, and difficulty starting. Has a new battery.

Would the ignition module cause this symptom - maybe a weak spark?? The Vortec of this year used an HEI distributor. I haven't worked on one of these in a while (have three cars with Optispark and another without distributor: LT and LS motors)

Thanks for any help

RT

**k.daddy1** · 09-02-2009, 01:28 PM

Check the vaccuum line to your fuel pressure regulator. If you have fuel in it, then replace the pressure regulator

**2ToNe04** · 09-02-2009, 02:05 PM

check the butterfly of the throttle body and make sure its clean, sometimes they tend to stick and it makes it hard to turn on.

if it is dirty you can buy this special spray to clean it off.

**Z71_guy** · 09-02-2009, 07:59 PM

second the fuel pressure regulator

**MrShorty** · 09-02-2009, 11:06 PM

Does it hold pressure when the pump shuts?

**alchemist1** · 09-04-2009, 12:27 AM

Originally Posted by MrShorty

Does it hold pressure when the pump shuts?

Yes. It drops just a little initially (from 48-49 tops to 40-45 psi and holds pretty well. By that observation, I sort of ruled out the anti-backflow valve inside the fuel pump. I am thinking either a restricted fuel filter or the fuel pressure regulator...

**MrShorty** · 09-04-2009, 10:22 AM

Is 50 psi the highest pressure you ever get out of it? I haven't tested it myself, but I've seen anywhere from 45 to 50 psi thrown out as the absolute minimum pressure that is needed to open the poppet valves. Spec key on engine off (KOEO) pressure is 60ish psi. On my '98, there's an small wire you can apply power to to run the pump. What does the pressure do if you get the pump to run continuously, or after cycling the key on then off (without starting) a few times?

What does the pressure do if you clamp off the return line? If you prevent the excess from returning to the tank, the pressure should jump well above spec (100 psi wouldn't be out of the question). If the pressure doesn't jump up, then that suggests a restriction in the supply line or a pump that is unable to generate sufficient pressure. If the pressure does jump up, that suggests that the FPR is opening too soon.

**alchemist1** · 09-05-2009, 10:04 AM

Great advice Mr.Shorty. Yes 50 is all I get, and I had already done the FP jumper thing (getting it to run continuously and also 'pulsing' it off and on. I bought a fuel filter and will put it on, but question I have is where do you pinch the fuel return line?

Thanks.

**MrShorty** · 09-05-2009, 10:50 PM

I'm not sure exactly where it's at, but I expect somewhere near where the fuel return line attaches to the motor and the frame is a rubber/flexible section. It's that section that you would clamp off.

**alchemist1** · 09-06-2009, 06:24 AM

Thanks again MrShorty for the good advice. I did see what you were talking about underneath truck, about 8 inches forward of where the filter is. I ran the pump today and pinched the line hard with my thumb (felt it deflect a lot). My son didn't notice any increase in pressure reading - do I need to clamp it off completely (e.g. a small c-clamp), or should my first test have told me something enough already?

Yesterday I changed out fuel filter and did not help. One more question- it looks like the fuel pressure regulator is 'hidden' under the plastic intake top. Presume you have to remove the top in order to check the vacuum line going to the FPR or to change out the FPR? Looks like you would have to remove supply and return lines and maybe use new o-rings?

Sorry for long post. Thanks for your patience.