Truck will not stay running

Tiny
SAUL CONDE
  • MEMBER
  • 1992 DODGE DAKOTA
  • 3.9L
  • V6
  • 2WD
  • MANUAL
  • 170,000 MILES
So the truck quit running on me.
Got it towed to the house. So it turns on, idles rough then shuts off. I tested the fuel pump and it is working great. Fuel filter is not clogged. I do not know if it is a sensor or what? It seems like it is not getting enough gas. Sometimes it idles smooth at around 90 rpm but if I give it gas then it backfires and shuts off. Need help ASAP as this is my only vehicle and rent is coming up. I don't have any special tools. Could it be my timing? Thanks!
Tuesday, April 16th, 2019 AT 10:09 AM

12 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,139 POSTS
Welcome to 2CarPros.

First, I need you to retrieve diagnostic trouble codes from the computer. It is simple to do and requires nothing but an ignition key.

https://www.2carpros.com/articles/retrieve-trouble-codes-for-chrysler-dodge-plymouth-odb1-1995-and-earlier-car-mini-van-and-light-trucks

I have to be honest, it does sound like a fuel related issue. Have you actually checked fuel pressure? Also, have you checked for major engine vacuum leaks? Although you don't have a fuel pressure gauge, most parts stores will lend or rent one to you. We really need to confirm it is within spec. Please keep in mind, you may get fuel but if the pressure is too low, the engine won't run or run properly.

Here is a link that shows how to check pressure:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

________________________

Here are the specific directions for your vehicle. The attached pictures correlate with these directions.

FUEL PRESSURE TEST
Dual Throttle Body Assembly
picture 1

Pressure Regulator And Vacuum Hose
picture 2

Fuel systems on these vehicles are equipped with a vacuum assisted fuel pressure regulator. With engine at idle speed, system fuel pressure should be approximately 214 kPa (31 psi) with the vacuum line connected to the regulator. With the vacuum line disconnected from the regulator, fuel pressure should be approximately 269 kPa (39 psi). This is 55-69 kPa (8-10 psi) higher.

1. Remove the protective cap at the fuel rail.

Fuel Pressure Test - Typical
picture 3

Connect the 0-414 kPa (0-60 psi) fuel pressure gauge (from Gauge Set 5069) to test port pressure fitting on fuel rail.

2. Note pressure gauge reading. Fuel pressure should be approximately 214 kPa (31 psi) at idle.

3. Disconnect vacuum line at fuel pressure regulator. Note gauge reading. With vacuum line disconnected, fuel pressure should rise to approximately 269 kPa (39 psi).

Fuel pressure should be approximately 55-69 kPa (8-10 psi) higher with vacuum line removed from regulator. If not, inspect pressure regulator vacuum line for leaks, kinks or blockage. If vacuum line checks OK and fuel pressure does not rise approximately 8-10 psi after disconnecting vacuum line, replace fuel pressure regulator.

NOTE: The fuel pressure regulator is not adjustable.

4. If fuel pressure exceeds 45 psi, check fuel return line for kinks or obstructions.

If the previous tests checked good, fuel pump pressure is correct.
Proceed to the Fuel Pump Capacity Test.

If pump pressure was low, proceed as follows:

1. Release fuel system pressure. See Fuel Pressure Release Procedure.

Quick Connect Fittings
picture 4

2. Disconnect the 5/16 inch fuel return line quick connect fitting on fuel rail near fuel pressure regulator.

Adapter Tool Connections - Typical
picture 5

Connect Fuel Line (Tube) Pressure Test Adapter Tool number 6539 (5/16 in.) between the disconnected fuel return tube and fuel rail.

Warning: the fuel system pressure in the following test may exceed 100 psi. Before starting test, verify good connections at ends of adapter tool 6539. Be sure tool is locked onto fuel rail and fuel return line. Pull firmly on ends of tool to verify.

3. Using the DRB II or an equivalent scan tool, activate the fuel pump and pressurize the fuel system. Refer to the scan tool manufacturers service manual for scan tool operation.

4. Momentarily pinch the rubber hose portion of adapter tool 6539. Pressure should rise to approximately 75 psi within two (2) seconds. DO NOT pinch hose for longer than five seconds.

If fuel pump pressure rises to approximately 75 psi within two seconds, pump is operating at its maximum and is correct.
Proceed to the Fuel Pump Capacity Test.

If fuel pump pressure does not rise to approximately 75 psi within two seconds, proceed as follows:

1. Release fuel system pressure. See Fuel Pressure Release Procedure.

2. Raise and support vehicle.

3. Disconnect fuel supply line at inlet (fuel tank side) of fuel filter. Connect Fuel Line (Tube) Pressure Test Adapter Tool number 6631 (3/8 in.) between fuel filter and fuel supply line.

Warning: the fuel system pressure in the following test may exceed 100 psi. Before starting test, verify good connections at ends of adapter tool 6631. Be sure tool is locked onto fuel filter and fuel supply line. Pull firmly on ends of tool to verify.

4. Using the DRB II or an equivalent scan tool, activate the fuel pump and pressurize the fuel system. Refer to the scan tool manufacturers service manual for scan tool operation.

5. Momentarily pinch the rubber hose portion of adapter tool 6631. Pressure should rise to approximately 75 psi within two (2) seconds. DO NOT pinch hose for longer than five seconds.

If fuel pump pressure now rises to approximately 75 psi within two seconds, but this pressure could not be met at the fuel rail, check for a plugged or restricted fuel filter. Also check the fuel supply line between fuel filter and fuel rail for kinks or obstructions.

_________________________________

Do these things first. I have owned Dakotas for the past 20+ years, so I should be able to get you through this. However, I do need you to check the aforementioned things so I know which direction to lead you.

________________________________

Let me know what you find.

Take care,
Joe
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Tuesday, April 16th, 2019 AT 10:45 AM
Tiny
SAUL CONDE
  • MEMBER
  • 7 POSTS
Which port would I hook the tester to?
I will see if I can get a hold of the tester for the gas pressure. I got a fuel pump from a junk yard. Put it in and idled okay for a little but then went right back to square one. Idles okay at 900 then if gas is applied it hesitates to gives gas then will backfire and shut off.
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Tuesday, April 16th, 2019 AT 11:02 AM
Tiny
SAUL CONDE
  • MEMBER
  • 7 POSTS
So I tested the fuel pressure and it is all within specs with the vacuum line on and without the vacuum line on. As far as the codes on the truck the only code that is popping up is code number 12. I also took off the sensor that is to the right of the throttle body and as you can see in the picture it is chipped. Could this be the problem?
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Tuesday, April 16th, 2019 AT 12:58 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,139 POSTS
Welcome back:

That appears to be the idle air control valve. Yes, it is what maintains engine idle speed. The broken part is a concern. Is it inside the throttle body?

I attached a picture for you to look at. Confirm that it is the part you removed.

Joe
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Tuesday, April 16th, 2019 AT 4:06 PM
Tiny
SAUL CONDE
  • MEMBER
  • 7 POSTS
So that sensor was the throttle position sensor I believe. Either way I replaced it and it is still doing the same thing. I am at a loss. Don't know what else to do.
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Tuesday, April 16th, 2019 AT 4:10 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,139 POSTS
The picture I sent is the idle air control valve. Are you able to get it to run if you lightly hold your foot on the throttle? If not, I need you to recheck for spark. Here is a link:

https://www.2carpros.com/articles/how-to-test-an-ignition-system

If there is no spark or weak spark, the distributor pick up coil is my primary suspect. It is located in the distributor itself.

Also, see if it will start for a couple seconds using starting fluid.

Let me know.

Joe
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Tuesday, April 16th, 2019 AT 4:27 PM
Tiny
SAUL CONDE
  • MEMBER
  • 7 POSTS
So it will idle fine right now at about 900 rpm. If I give it gas when it sounds like it is going to shut off it will hesitate (like gas is not going through) and then rev real high like all the gas shot out at once. Backfires like I am in a shoot out in Compton and then shuts off.

If I leave it alone to just idle then it will shut off after about one minute
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Tuesday, April 16th, 2019 AT 5:08 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,139 POSTS
Welcome back:

Did you check for vacuum leaks?

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Also, I need you to open up the distributor and check the pick up coil (referred to as a cam sensor in the manual). See if there is rust or dirt build up on the pulse ring or if the sensor itself. If it appears to be in poor condition, replace it and clean the pulse ring with emery cloth. (see picture 1)

Next, if that is good and you feel, I need you to get a test light and check engine timing to determine if it is off. This engine came from the factory without any type of timing chain tensioner. The timing chains stretch, usually you will hear it make noise, and they can jump time. The backfire has me questioning timing or the sensor I mentioned. I had a 90 with the same engine and when I decided to replace the chain because of noise, they offered a tensioner as optional. It never made a sound after that.

Let me know what you find.

Joe
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Wednesday, April 17th, 2019 AT 5:41 PM
Tiny
SAUL CONDE
  • MEMBER
  • 7 POSTS
So I did open the distributor the pick up coil looks good but I did attach a picture of the distributor cap which looks worn to me (almost two years old along with the whole distributor assembly).

Aldo attached a picture of the sensor I replaced which is the throttle body sensor.
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Wednesday, April 17th, 2019 AT 5:52 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,139 POSTS
The cap does look worn, but I don't think that is the problem unless it is cracked. However, that may cause a backfire or misfire, but normally, not a stall. Try the test with the timing light. If spark is an issue, you will see an erratic flash. At that point, we will need to check the coil as well as the sensor I mentioned. Also, it will give us a good idea if timing may have jumped.
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Wednesday, April 17th, 2019 AT 6:14 PM
Tiny
SAUL CONDE
  • MEMBER
  • 7 POSTS
Okay, cool. I will try the timing and the sensor you were talking about is which one just to be clear? Pick up coil looked good. Is there another coil I should check?
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Wednesday, April 17th, 2019 AT 6:18 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,139 POSTS
The pick up coil is referred to as a cam sensor in the manual. It is the one under the plastic cover inside the distributor. I forgot to attach the picture, so here it is.

Joe
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Wednesday, April 17th, 2019 AT 6:53 PM

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