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No primary electric to fuel pump
01-08-2012, 05:18 PM
Post: #1
No primary electric to fuel pump
1998 Plymouth Breeze - Standard 5 speed - 2.0 engine Vin C - 179,560 miles - Central Arizona Mountains (3500 ft)

I can start my car by pumping the gas and then keeping the rpm above 2000 it runs without pumping. When I go below 2000 rpm, it stalls out and won't idle. Acts like it's starving for gas. I don't have a pressure Gage, but at the test valve only a trickle of gas comes out. I put in a brand new fuel pump last week thinking that was the problem. But Same!

I now have the fuel pump in a test mode. I took the gas tank and the fuel pump out. I put a three gallon open top tub of gas in the trunk with the fuel pump plugged in with the bottom 2/3 submerged in gas. I have a short hose on the fuel filter connection running back into the tub.

The car is a standard and requires having the clutch engaged to start the fuel pump and the starter. The starter works but the pump doesn't come on when you turn on the key and engage the clutch ( the clutch switch only has two wires to and from it). When you use the starter, the fuel pump squirts gas in rhythm with it trying to fire.

I can't find any loose or disconnected wires. It has 4 Relays, all the same type and number. I rotated them with no change in any of the systems.

The only fuse box I can find is under the hood and all fuses are clear bodied and look fine.

Is there a second inline fuse for the fuel pump? If yes, where do I look for it? If no, where do I start looking for the problem?

Hope someone can help!
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01-08-2012, 05:42 PM
Post: #2
RE: No primary electric to fuel pump
Every injected car I have ever worked on gets it's power signal from the ECM with the exception of when the starter is cranking. That part goes around the ECM till it fires up. The initial signal from the ECM is about 2 seconds when the key is first turned on, which primes the system. If you crank and release the key without starting it should power up for another 2 seconds then shut off.

Since the car is 13 years old I would be checking the voltage at the pump and looking for a poor connbection on either the ground or power side of the circuit. Somewhere during your tests you need to figure out which relay is for the pump and do some pin checks. One pin is hot all the time, one pin is switched from the ECM, another pin is ground and one more pin will be power to the pump. The idea is to locate the ECM signal. If none is present then either you have a bad connection farther up the line or the ECM itself may be bad.

As for the low pressure, hard to make any assumptions without a gauge. The flow after the pressure regulator is not much so it's impossible to know if this is really low presure or just low looking because you are creating a major leak. In this case you need hard numbers to work with. There is no guessing for a proper diagnosis.

Let us know what else you find and possible we can piece this together. In the meanwhile, be aware that working with an open bucket of gas inside the car can be rather dangerous. All it takes is one spark!
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01-08-2012, 08:22 PM
Post: #3
RE: No primary electric to fuel pump
I didn’t see anywhere that the fuel filter was changed. If it is plugged the fuel won’t reach the engine even if the pump is running.

Thanks for using the forum,
Garner

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01-09-2012, 12:25 PM
Post: #4
RE: No primary electric to fuel pump
(01-08-2012 08:22 PM)Garner Wrote:  I didn’t see anywhere that the fuel filter was changed. If it is plugged the fuel won’t reach the engine even if the pump is running.

When I first set up the test mode, I did not include the filter. No changing of the system occurred. Same with filter included.

Thank both of you for your responses. I have been asking this same question all over the net.

This morning I received two responses that both said I was describing a MAP sensor failure. I'm trying to confirm that now.

Thank You
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01-09-2012, 12:42 PM
Post: #5
RE: No primary electric to fuel pump
Connecting a scanner and reading "live data" may help you with the diagnosis of a bad MAP sensor, but so will a pressure gauge on finding out exactly what the fuel pressure is while running. At least if you know the reading is good (50 - 60 psi) then you know where the problem is not and you can move to the next phase.

Cars are not what they once were and without more information you are just throwing parts at it without a sure fix.
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01-09-2012, 07:02 PM
Post: #6
RE: No primary electric to fuel pump
OK. Could you guys confirm something for me?

I've did a test on the MAP Sensor connection, using help from this site:

http://easyautodiagnostics.com/chrysler_...tics_1.php

I have confirmed that 5.0 volts of power is going to the Sensor connection.

I have confirmed 11.5 volts from the Ground connection at the Sensor, to the hot side of the battery.

I have confirmed 0.0 volts coming out from the Sensor. Does this indeed confirm that the Sensor is BAD? And does a totally none working MAP Sensor correspond with the problem I'm having?

I'm in my 60's and all my personal repair knowledge is from car's much much older!

Thank You
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01-09-2012, 10:34 PM
Post: #7
RE: No primary electric to fuel pump
You really can't confirm anything unless you can get the varied readings from a varied vacuum sorce. (test #1 on that page)

If you don't have a vac pump or a vac gauge you might try using a piece of vac hose and sucking on it while alternately blocking it with your tongue. Yeah, it sounds a bit cheesy but most people can work up around 10 - 12 inches of vac this way and that would be a start at finishing the diagnosis. It's a trick I picked up about 45 years ago when I was still wet behind the ears. (wink, wink)

Now, a little theory so you can understand a bit more on how the system works....

The MAP sensor looks at manifold vacuum (throttle / load) and allows fuel to be injected based on how much is needed. Combine this with the TPS (throttle position sensor) and the MAF (Mass Air Flow) the computer knows where your foot is on the gas and how much load the engine is seeing and at what RPM. (yes, the computer sees that as well) This works the same as an old carb in that as load / speed increase there's more fuel flowing. The MAP sensor is in charge of both mixture and enrichment, similar to the old accelerator pump and main jets, when you step on the gas. If the MAP sees low vacuum it goes rich so the engine doesn't stumble and tapers off as the engine speed goes up due to the vac changing as the load decreases. Basically if the MAP isn't working the car will stumble like a dirty carb, although low fuel pressure can do the same thing. (back to the pressure test readings)

Yes, the system is a bit more complex than old fashion carburators, but this is how they squeeze the extra MPG and gain cleaner exhaust, cleaner engine oil, better cold starting, and longer engine life. It's all related.

Oh, while we are on the topic of monitoring vacuum, have you examined all of the vac hoses? I can't tell you how many times I have seen someone barking up the wrong tree only to have missed some bad hoses that would have cost $5 to fix. If it doubt, spend the few bucks and replace ALL of them before going further!
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