Cold start VS warm start

[kenh]

When I start my 1990 K1500 with a 5.7 with a cold engine it rolls over for 3 to 5 (maybe less) seconds before it catches and fires. Same after work after setting for 8 hours or more.

When warm it starts instantly. Well damn quick, maybe one revolution or less. Even after setting for 1/2 hour or so.

It never fails to start even when it's below 20 degrees. Temp doesn't seem to matter. Could be 80 out and the same delay. Same time to first fire when cold.

Any ideas what would cause this or is it just the nature of the beast. I'm used to more "modern" FI.

Thanks!

Ken

 

[454cid]

Next time you start it cold, turn the key to run and let the pump prime, then turn it back off, and them prime the pump again before finally starting it.

 

[Nad_Yvalhosert]

Yup. Prime it first on cold start.

 

[kenh]

Next time you start it cold, turn the key to run and let the pump prime, then turn it back off, and them prime the pump again before finally starting it.

Done that and no change. Was first thought to prime the system.

Ken

 

[454cid]

I don't have any experience with TBI engines. I'm still thinking a fuel supply issue, as that's what it was with my Vortec. I'd start checking fuel supply for pressure and bleed down with the engine off, as my initial suggestion was a crude way of testing that. You don't have a factory test port on a TBI engine, so it's not as easy as it is on my Vortec 454. Someone with TBI experience may have better suggestions.

I suppose it would be pretty easy to tell if your injectors were leaking, since they're sitting relatively exposed.

I wonder if it could also be an engine temperature thing.... do you have the ability to read what your CTS is seeing?

 

[618 Syndicate]

If I were to hazard a guess, I'd think that the fuel pressure is bleeding off and it's taking a few cranks to get it back.

 

[PlayingWithTBI]

When I start my 1990 K1500 with a 5.7 with a cold engine it rolls over for 3 to 5 (maybe less) seconds before it catches and fires.

That's pretty much common. FWIU, when you turn on the key the fuel pump will run for ~2 seconds. Then if you turn the key off and back on it won't prime again, there's a delay for somewhere around 3 - 5 seconds before the ECM will turn it back on so, when the engine is cold it'll take a few seconds until the oil pressure switch turns on the pump. Now, after the engine is warmed up (or semi warm) the "hot fuel module" will give you fuel immediately. I'm thinking this is to prevent starting the engine after sitting for too long before getting some oil circulating throughout.

Here's the fuel pump schematic with the oil pressure switch

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Here's the hot fuel module

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Mine's the same way, when it's warm the engine doesn't even turn over much more than 1 revolution before it fires. HTH

 

[PlayingWithTBI]

If I were to hazard a guess, I'd think that the fuel pressure is bleeding off and it's taking a few cranks to get it back.

The TBI system isn't like the Vortec. It bleeds off immediately upon key off (or fuel pump shut off), where the Vortec has a check valve that holds pressure.

 

[618 Syndicate]

The TBI system isn't like the Vortec. It bleeds off immediately upon key off (or fuel pump shut off), where the Vortec has a check valve that holds pressure.

Thanks for clarifying.

 

[PlayingWithTBI]

Thanks for clarifying.

No Problem, glad I could help