Mpfi fail?

[bldn10]

2 1/2 years ago I did the MPFI conversion on my '99 Tahoe. About 6 mos. ago it started giving me a hard time starting it. It would turn over OK but not hit, and sometimes made a noise like a backfire under the hood. Just like it did before the conversion. I thought this was going to be a permanent solution. It finally got so it was not worth fooling w/ and I bought an '02. I want to sell this '99 but it will not start now. Or I should say it will not stay started. It will hit but immediately dies. If I pour a bit of gas in the TB it will start and run a few seconds on that gas. It does not seem to be getting gas. I changed the fuel filter and can hear the pump running.

Any ideas?

 

[OR VietVet]

Fuel pressure output and aftermarket MPFI fuel pressure needs?

 

[bldn10]

Fuel pressure output and aftermarket MPFI fuel pressure needs?

Are you suggesting that the MFPI may require higher fuel pressure than the pump provides? In researching whether to do the conversion to begin w/ I don't recall any mention of that. It was installed by a shop and they did not recommend a new pump.

And keep in mind that it ran for almost 2 years just fine. Of course, the pump could be failing.

 

[OR VietVet]

Just asking because I don't know. Makes sense to me that TBI needs less pressure than MPFI and maybe you had to add an additional pusher pump when installed or different pump altogether. That was not explained in original post so thought I would ask. Ran ok for 2 years and now need to find out what dropped out to cause the current problem. Check fuel pressure and see if it matches what the system requires.

 

[99Vortec]

So you did the CSFI to MPFI upgrade?

I see TBI mentioned on above post which confused me.

Definitely check your fuel pressure.

You can hear the fuel pump running when you cycle the key on and off?

If you slightly depress the fuel system's "Schrader Valve" after cycling key, does any fuel release?

I would definitely check fuel pressure as a starting point.

Gl.

 

[ccapehartusarmyINF.(ret)]

MPFI ?
Many People Fart Indoors
did you know that bosch invented multi port fuel injection first used in several german aircraft during world war 2 this was a major advantage over the rolls royce merlin engine used by the brits because it was carberated and the engine would stall during a negative G dive

 

[bldn10]

"If you slightly depress the fuel system's "Schrader Valve" after cycling key, does any fuel release?"

Where is that valve?

For some reason I'm not being notified of replies.

 

[99Vortec]

Ideally, you would want to hook up a fuel pressure test gauge here.

(Shown in pic with blue dot on cap.)

 

[bldn10]

Tested fuel pressure and it zips to 62 w/ key on. Engine will start w/ starting fluid but not keep running. What next?

 

[OR VietVet]

As long as your fuel pressure stays good with the engine trying to run I would say you have lost injector pulse. The injectors are not firing fuel in to the cylinders.

---------- Post added at 03:57 PM ---------- Previous post was at 03:54 PM ----------

typically caused by ecm/pcm failure.

---------- Post added at 03:59 PM ---------- Previous post was at 03:57 PM ----------

Ignition module or pickup coil problem? They work together to supply the square wave signal/on-off signal for the injectors.