DFlintstone

To criscross with Skips original suspicions, Checking the voltage out the rear of the ballast resistor (directly to the pump), or seeing if jumping power there helps might be something easy to rule out.

Of course checking the pressure would trump anything like that.

bdcontraplayr

It did pop out from the intake, I think it happened before I took the intake manifold off to change the gasket. And it stalls when you give it more gas

cruiser54

Check the fuel pressure!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

DFlintstone

OK, gotcha...but I didn't mean "more", I meant floored. (past 80% throttle it ignores a bunch of sensors)

bdcontraplayr

I did back in the beginning of the summer and it was still around 31psi.

DFlintstone

Mine did much like you describe for about a year before I found it, (or had joined the forum). It would dog and backfire when I gave it throttle, but still go like hell if I floored it.

bdcontraplayr

Can't floor it from every stop sign

DFlintstone

It's a check, not a strategy. (see post # 259)

Mill

Soooo, where are we on all this? Just curious.
Mill

bdcontraplayr

Does anyone know what the volume output of the fuel pump should be? I have a feeling that the fuel pressure regulator is putting air into the fuel rail and not enough fuel is getting to the injectors when the motor is under stress from a stop. I don't see any leaks of fuel but I have noticed that the fuel line has air in it when I depressed the valve on it to relieve the pressure when I changed the intake gasket

DFlintstone

Howdy BD. So it's runnen. you driven it? The fuel in the system under 30# plus won't let air in. (a ruprure in the regulator would mean fuel in it's vacuum line). Since the pump is submersed, I'm not seeing air getting in there.

Probably anywhere that could let air in while it's sitting with no pressure, would leak fuel with it under pressure. Small chance though that an O ring could seat under pressure, but leak under a vacuum.

Then of course there is vapor lock, the fuel getting so hot it boils.

I think flow is something like a quart in 30 secs...I'll take a whack in finding that in the FSM....

DFlintstone

OK it says a liter a minute (close enough to a quart), with the return line pinched off. Says to check the filter and inlet "sock" if the flow is low.

Pressure is 39# with the vacuum line off the regulator, about 10 less with it on. (I think posted that backwards somewhere recently)

firehawk618

Everything you describe sure sounds like a malfunctioning MAP sensor.

Yeah I know it's been replaced already.

Maybe it's not the sensor, maybe your harness is damaged?

I did skip over pages 13 through 17 though....

It would make sense why it runs super crappy until you hit WOT. Once you hit WOT you're also using as much fuel that's being injected as if the MAP were reporting zero vacuum ......if that makes any sense.

Maybe the MAP sensor is the INCORRECT one for your vehicle...??

Also, from what I have read on this forum so far ECU failure is extremely unlikely but consider this....

Since the PO did such a LOVELY job cutting out and splicing that connector do you think said person could have either got some wires wrong or even worse accidentally applied power / ground to the wrong wires at one time in essence killing the ecu.....causing intermittent issues?

I cannot count how many vehicles I have repaired in the past where other "mechanics" were backprobing and applying either voltage or ground to wires that should not have ever had + or -12 applied to them which in turned fried various parts of ecu's.

bdcontraplayr

Hey guys, I just wanted to update you on my Laredo.

Since I last posted here, the only thing I did was replace the fuel pump assembly. I did this on hopes and prayers because I just wanted too. Since then its been running! I have had it cut out once, but I did another seafoam treatment to it and it seemed to cut that problem out. The only problem I can find now is a low idle of 500rpms when it's warmed. (Not really sure what the idle should be at normally.)

I just wanted to say thank you to all of you. I'm going to edit my first post so if someone is having the same issue they can look into this. The fuel pump was original, and the damn thing has 340,000 miles on it.

Here's to another 340,000 miles, thanks CF!

cruiser54

Glad to hear.

Your low idle could be caused by numerous things. What have you done so far to address it? Any of my Tips?