Mechanics

LOSS OF POWER

1990 Dodge Omni

Engine Performance problem
1990 Dodge Omni 4 cyl Front Wheel Drive Automatic 21000 miles

I recently purchased a 1990 dodge omni with 20k miles, garage kept and rarely used over the past 10 years. Most use was merely running engine less than 2k rpm. Engine runs fine most of the time. Sometimes when coasting or decelerating it loses power and the only way to make it continue is by pumping the accelerator as rapidly as I can with poor results. I may be able to limp along at 20-30mph. If I let is sit for a few minutes, or hours it will get over it and resume normally. When this event takes place the tack will show dramatic fluctuations and oscillate between 1-2k rpm. Thinking possibly, the fuel pump or sock was an issue, I changed the sock. I changed the fuel filter. No change. I installed a gauge in a tee and measured fuel pressure, 18lbs. The book says normal is 34-38 lbs. I pinched return line and pressure went to 38lbs. There is a receipt in the glove box indicating the fuel pump was replaced within the past couple years. I replaced the fuel pressure regulator, no change. The vacuum lines seem to be flexible with no brittleness. It also appears to me all lines and electrical connections are in tack. What's next?
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Bruce18
April 25, 2009.



If you already replaced the FPR, then at 18psi, the pump is again the problem. If it is a vauum operated regulator, is vacuum present at idle?
Is your check engine light on? If yes turn the key from off to on three times, on the fourth one leave it in the on position, count the flasshes.22 would flash as 2 blinks, then a short puase, then 2 more blinks. If several codes are stored, the pause is longer between codes, code 55 will be the last code. Do this and post all codes found.

Merlin2021
Apr 26, 2009.
I don't know how the FPR is operated, no wires and 2 ports on the bottom, 1 larger than the other, bolted in the center of throttle body. The engine check light comes on and will reset after engine is off for some time. The code produced is 35 which the book says it is the cooling fan relay circuit. If engine is cold the automatic choke works well so I'm thinking vacuum is ok. As to the fuel pump, the pressure increases to the normal 38lbs if the return is restricted by a pair of pliers.

Tiny
Bruce18
Apr 26, 2009.
I show a fuel pressure of 14 psi for non turbo 4 cyl, turbo and six cyl are higher, what engine size? Turbo?
TBI FUEL PUMP TEST Release fuel pressure. See FUEL PRESSURE RELEASE in this article. Disconnect 5/16" fuel supply hose. Connect fuel system pressure Gauge (C-4799-A) between fuel supply hose and engine fuel line. 1. Turn ignition on. Using DRB-II (C-4805), activate fuel pump. See FUEL PUMP PRESSURE SPECIFICATIONS table in this article. If fuel pump pressure is at specification, fuel system is functioning properly. 2. If fuel pressure is not to specification, record pressure. Install fuel pressure gauge in fuel supply line at rear of vehicle between fuel tank and fuel filter. 3. Using DRB-II, activate fuel pump. See FUEL PUMP PRESSURE SPECIFICATIONS table in this article. Record pressure reading. If fuel pressure is 5 psi (.4 kg/cm 2 ) higher than first pressure reading, replace fuel filter. 4. If no change in pressure reading is observed, gently squeeze fuel return hose. If fuel pressure increases, replace fuel pressure regulator. If no change in fuel pressure is observed, problem is plugged fuel pump filter sock or defective fuel pump. 5. If fuel pressure is more than specification, remove fuel return hose at rear of vehicle. Connect an extension hose to return hose. Place hose in an approved container with at least a 2 gallon capacity. 6. Using DRB-II, activate fuel pump. If fuel pressure is now within specification, check in-tank return fuel hose for kinking. Replace fuel tank assembly if in-tank reservoir check valve or aspirator jet is plugged. 7. If fuel pressure is still more than specification, remove fuel return hose from throttle body. Connect a substitute hose to throttle body return nipple. Place other end of hose in an approved container. 8. Using DRB-II, activate fuel pump. If fuel pressure is at specification, check for a restricted fuel return line between throttle body and fuel tank. If no change was observed, replace fuel pressure regulator. 9. NOTE: Perform fuel pump test with fuel tank at least half full. Before disconnecting a fuel line during testing, repeat fuel pressure release procedure. Page 1 of 1 BASIC TESTING -1990 Dodge Omni America 4/27/2009


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FOUR CLYINDER:
4-CYLINDER PFI FUEL PUMP TEST Release fuel pressure. See FUEL PRESSURE RELEASE in this article. Remove cap from service valve on fuel rail. Connect fuel system pressure Gauge (C-4799-A) to service valve. 1. Turn ignition on. Using DRB-II, activate fuel pump. See FUEL PUMP PRESSURE SPECIFICATIONS table in this article. If fuel pump pressure is at specification, fuel system is functioning properly. 2. If fuel pressure is not to specification, record pressure and remove gauge. Using DRB-II, activate fuel pump. Ensure no fuel leaks from service valve. Install cap on service valve. 3. If fuel pressure is not to specification, install pressure gauge in fuel supply line between fuel tank and fuel filter at rear of vehicle. Using DRB-II, activate fuel pump. 4. Record pressure reading. If fuel pressure is 5 psi (.4 kg/cm 2 ) higher than first pressure reading, replace fuel filter. If no change in pressure reading is observed, gently squeeze fuel return hose. 5. If fuel pressure increases, replace fuel pressure regulator. If no change in fuel pressure is observed, problem is plugged fuel pump filter sock or defective fuel pump. 6. If fuel pressure is more than specification, remove fuel return hose at rear of vehicle. Connect an extension hose to return hose. Place hose in an approved container with at least a 2 gallon capacity. 7. Using DRB-II, activate fuel pump. If fuel pressure is now within specification, check in-tank return fuel hose for kinking. Replace fuel tank assembly if in-tank reservoir check valve or aspirator jet is plugged. 8. If fuel pressure is still more than specification, remove fuel return hose from pressure regulator. Connect a substitute hose to fuel pressure regulator. Place other end of hose in an approved container. 9. Using DRB-II, activate fuel pump. If fuel pressure is at specification, check for a restricted fuel return line. If no change was observed, replace fuel pressure regulator. 10. NOTE: Perform fuel pump test with fuel tank at least half full. Before disconnecting a fuel line during testing, repeat fuel pressure release procedure. Page 1 of 1 BASIC TESTING -1990 Dodge Omni America 4/27/2009

Merlin2021
Apr 27, 2009.
I see in your fuel pump spec table the TBI fuel pump should be 14lbs, mine is reading near 18lbs. I see that as a non issue. My haynes manual says 34-38 lbs but that my well be for a turbo engine. My engine is a 2.2 non turbo. The book doesn't specify which set up, so I concluded it was the same for all applications. This information leads me to believe the fuel pump is operating nominally. As to the check engine code, I seeing 35 which I mentioned earlier. I drove the vehicle today and after 15-20 miles it began the same issue, loss of power @ about2k and I pumped pedal to maintain minimal speed. Prior to this event I was traveling 3k or more @ 65mph.

Tiny
Bruce18
Apr 27, 2009.
On an old car thats been sitting in storage, look at the EGR when it wont start or its running rough, it may be partially stuck open.

Merlin2021
Apr 29, 2009.