95 Suburban hard cold start

[notagearhead]

I own a 1995 suburban, 5.7 L, 4x4

Last week it started to not want to start. I have to start cranking the
engine then slowly depress the accelerator to about half way down before
the engine catches and runs. When it does start it seems to only start
on a few cylinders, but then the others all kick in within a few seconds.
When cranking the engine, the starter will sometimes stop dead then
resume cranking and the engine also back fires and knocks. Once the
engine is started it runs great (lots of power, idles fine). Hot starts are
similar to cold starts.

I have replaced the cap, rotor and plugs. The wires are only 2 yrs old.
I checked the timing and it sits solidly at 0 deg, so I don't think it is the
timing chain. I have also replaced the fuel pump, ignition switch, fuel filter,
EGR valve and control, and exhaust system within the last 3 months. It
ran fine until last week. Any ideas?

Thanks for your help in advance.

[flht]

What kind of pump did you use, I had this problem on a 97 burban and MT2000 helped me out. The fuel pressure should be 62 PSI when you turn on the key and 45-47 running pressure. The pressure should also hold when you shut the engine off. (a pressure gauge is a good investment) I had 54-57 PSI and mine was a pain in the A$$ to start. I went a got a better high performance (for what HP is worth) and now it starts and runs fine.

[Pats1999]

flht - 97's are MPFI Vortec engines. His 95 is TBI and they run a very low fuel pressure compared to those. His is around 8-11 psi, though don't quote me on that. Though you have to have special tool to check TBI fuel pressure.

When it does start though, do you see a small amount of black smoke out the exhaust? It sounds like one of the fuel injectors is leaking giving you a rich condition at startup. - Hence having to open the throttle some to give it more air. I had a '88 Pontiac GTA that did this to me. Only difference was the hot starts were really tough. So I can go the other way also with this:

If it was a bad fuel pump or one that is bleeding down, you wouldn't have enough fuel pressure at startup. Turn the key on and don't start the engine and see if you hear the fuel pump building pressure. Turn the key off and wait 10 seconds. Turn it back on.. What I am trying to do is pressurize the system to see if it starts better or the same.

Either way, I am trying to help you decide if it's a rich (leak) or lean (something is bleeding down the fuel system) condition at startup.

Pat

[Pats1999]

Well, didn't notice this was a post from last month.. May already been fixed..... Oh well. Pat

[Jerscarcare]

Even though this is an old thread I thought I would give MHO, I have a 96 Suburban 5.7 that had the same problem, I replaced the fuel pressure regulator when I did the Intake manifold gaskets and WOW she starts right up no hesitation at all. So my vote is - replace fuel pressure regulator I hear it is common problem for these engines.