L29 454 MPFI Spider Conversion Questions

[ErikL]

Hi everyone,

I've only had my truck ('99 c3500, L29 454, ~127K miles) for a few months. I've been reading up on the forum about the MPFI Spider conversion and have some questions specific to the L29.

6 weeks ago when I was cruising on the highway at 60 MPH the check engine light came on. When I scanned it it showed codes P0172 & P0175 (System Too Rich Bank 1, System Too Rich Bank 2). The LONGFT1 was -14.1%, LONGFT2 was -17.2%. Looks like the ECU is consistently trying to reduce the fuel injected. I have noticed that exhaust smells rich when idling. I have not had any drivability issues. Truck starts perfectly when cold or hot. Fuel mileage has been ~10MPG in the city (unloaded), 13-15MPG on the highway (unloaded), and 7MPG on the highway (towing 6000 lbs fifth wheel). I cleared the codes and they haven't come back in the last couple hundred miles of driving and towing.


From what I see, I think they injectors are not leaking. I'm thinking the CPI Spider could be upgraded. The parts that I've seen referenced (i.e. AC Delco 217-3029) all say they fit the 5.7 Vortec, but never state that they fit the 7.4 L29.

My questions for those with the knowledge are:

Can I use the upgraded MPFI on the L29? Most state that they are only for the 5.0 or 5.7 L.
Has ACDelco 217-3029 been superseded by 19210687?

Thanks

 

[stutaeng]

Well, the spider injector setup was only on the 4.3/5.0/5.7, not on the 7.4. You already have MPFI. However, the 7.4 injectors are known to fail, based on what I've read here. And replacements are not inexpensive.

Are the fuel trims from the freeze frame? Can you monitor them in live stream? What are they in idle mode? What about when you rev up the engine? Can you also monitor O2 sensors in live stream? If O2 are fine, leaking injectors and/or FPR could be a problem. There's way to test them before condemning them.

 

[ErikL]

Well, the spider injector setup was only on the 4.3/5.0/5.7, not on the 7.4. You already have MPFI. However, the 7.4 injectors are known to fail, based on what I've read here. And replacements are not inexpensive.

Are the fuel trims from the freeze frame? Can you monitor them in live stream? What are they in idle mode? What about when you rev up the engine? Can you also monitor O2 sensors in live stream? If O2 are fine, leaking injectors and/or FPR could be a problem. There's way to test them before condemning them.

Thanks for clarifying that the 7.4 already has the MPFI! So a potential upgrade path would be to replace the injectors (i.e. fiveO Bosch 4-hole injectors) and maybe the fuel pressure regulator?

I'm pretty sure my cheap scanner only captures freeze frame (no live stream). Will borrow my friend's scanner. Pics attached from when it threw the codes.

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[stutaeng]

Thanks for clarifying that the 7.4 already has the MPFI! So a potential upgrade path would be to replace the injectors (i.e. fiveO Bosch 4-hole injectors) and maybe the fuel pressure regulator?

I'm pretty sure my cheap scanner only captures freeze frame (no live stream). Will borrow my friend's scanner. Pics attached from when it threw the codes.

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Yes.

Invest in a basic fuel pressure guage. It's a must for basic diagnosing. Also watch a few videos on testing FPR and injectors, as well as fuel trims. I've posted links to a few videos before.

Here's what a stuck open injector does. Doesn't sound like you have this gross leak condition, but it helps to visualize what's going on: Minute 17:00

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Injector balance test:

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A much longer, technical theory video:

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Keep us posted.

 

[88monteSS]

Thanks for clarifying that the 7.4 already has the MPFI! So a potential upgrade path would be to replace the injectors (i.e. fiveO Bosch 4-hole injectors) and maybe the fuel pressure regulator?

I'm pretty sure my cheap scanner only captures freeze frame (no live stream). Will borrow my friend's scanner. Pics attached from when it threw the codes.

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If you're in there to do injectors you might as well do the regulator too.

Sent from my XT1254 using Tapatalk

 

[8T7K5]

Replace the regulator while you're in there. I'd consider doing the lower intake gaskets too, they're known to leak. As for replacement injectors, go with the Bosch on 5-0s website or you can Google the part number. I've seen them on Amazon occasionally for less. When you replace the injectors have some small black zip ties ready, you will break some of the plastic tabs holding the clips unless you're extremely careful.

 

[ralmo94]

Old thread I know, but a good idea to replace the vacuum hose on the regulator to.