1989 Dodge Truck Loss of power on hills

GREATSTUFF

MEMBER
1989 DODGE TRUCK
V8
4WD
AUTOMATIC
110,000 MILES

318 V-8 TBI
Wires are fairly new, plugs look good, burning clean.
I removed the air pump and most of the hoses.
Trying to plug the EGR port on rear of exhaust manifold, but it keeps blowing out.

The truck loses power when going up a hill and I press on the accelerator. If I let up on the pedal it starts to run better. Checked the fuel pressure and is within spec.
Found out there is no vacuum at the fuel pressure valve.
Is this a faulty throttle body that Hayes repair manual talks about? I tried cleaning the vacuum nipple out and the port goes through to the throat of the Throttle body.
Truck has always had a slight miss at idle.
Any help is appreciated

5 Replies

RASMATAZ

MECHANIC
75,992 POSTS

You need that vacuum at the fuel pressure regulator otherwise the fuel system will not function right and also check the catalytic converter if its clogged-up-Do a backpressure test on the exhaust system or disconnect the exhaust pipe on the exhaust manifold and road test for power.

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Sunday, June 20th, 2010 AT 5:31 PM

GREATSTUFF

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5 POSTS

I am aware that vacuum is needed for the fuel pressure valve to work since it has an internal diaphragm. I guess my question would be how can I get vacuum? There is good vacuum on the front of the Throttle body for the
sensor on the air cleaner. Will a plugged converter cause loss of vacuum on the rear of the Throttle body and not on the front, or is there a defective throttle body casting?

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Sunday, June 20th, 2010 AT 6:22 PM

RASMATAZ

MECHANIC
75,992 POSTS

There is good vacuum on the front of the Throttle body for the sensor on the air cleaner, try teeing in and see if it works-The Cat will caused a low vacuum-the engine is not breathing properly can be verfied by backpressure test or by a vacuum gauge

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Sunday, June 20th, 2010 AT 6:30 PM

GREATSTUFF

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5 POSTS

O.K. Took your advice. I looked under the truck and there is no catalytic converter. I tee'd into the vacuum line on the front and the truck surges up and down when idling. It will almost stall and then catch and run and then almost stalls, etc. I talked with a local mechanic and he suggested taking the fuel pressure reading while driving, sure enough the fuel pressure drops when accelerating under load and the truck bogs down or looses power. He suggested the fuel pump being weak.
I suppose that will be the next project, trying to drop the fuel tank without breaking the 22 year old bolts.
The first thing that happens is a piece of dirt in the eye, next is a smashed finger or other body part.

I suppose tearing the throttle body off and cleaning the carbon out will also be in the cards.
Thanks for your help

Paul

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Monday, June 21st, 2010 AT 5:38 PM

GREATSTUFF

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5 POSTS

Still working on the truck, waiting for the filter sock that goes on the fuel pump. The clamp that holds the fuel pump/fuel gauge assy. Was broken. May have to improvise since the shop can't get them anymore. Have to make 2 new hangers for the tank, can't get them from the store either. Hope the pump is the problem.

Thanks again.