uneven running, fuel pressure issue?

autoloclys · 07-29-2021, 10:22 PM

having an annoying issue but so far it hasnt left me stranded.

In normal driving on the road, the engine in my '92 240 will occasionally stumble a little, its most noticeable between 1500-2000 rpm. Idle is smooth and above 2000 rpm the stumble is either not there or not noticeable

both fuel pumps are new since i bought the car and seem to be running (i can hear them when i check), Fuel pressure regulator also seems fine, no fuel in the vacuum line. and all the fuel lines between the tank and the engine have been replaced, though the return line is hose and not hard pipe

is it possible the intank or under car fuel pumps are running but not supplying sufficient pressure for certain conditions? neither one is a volvo part, but i would expect them to work or not work, rather than lose pressure slowly or intermittently.

or am i totally up the wrong tree with the fuel system?

James M · 07-29-2021, 10:47 PM

mattd1205 · 07-30-2021, 02:31 AM

I’d check for codes first if you haven’t already. If you suspect a fuel pressure issue, throw the autozone rental fuel pressure gauge on there. It doesn’t come with the fittings you need but you can cut up a fuel rail and part of the fuel line from a junk Volvo at the junkyard to make an adapter that will plumb into the tee fitting that comes with the gauge kit.

Otto Mattik · 07-30-2021, 02:39 AM

Quote:

Originally Posted by autoloclys

having an annoying issue but so far it hasnt left me stranded.

In normal driving on the road, the engine in my '92 240 will occasionally stumble a little, its most noticeable between 1500-2000 rpm. Idle is smooth and above 2000 rpm the stumble is either not there or not noticeable

both fuel pumps are new since i bought the car and seem to be running (i can hear them when i check), Fuel pressure regulator also seems fine, no fuel in the vacuum line. and all the fuel lines between the tank and the engine have been replaced, though the return line is hose and not hard pipe

is it possible the intank or under car fuel pumps are running but not supplying sufficient pressure for certain conditions? neither one is a volvo part, but i would expect them to work or not work, rather than lose pressure slowly or intermittently.

or am i totally up the wrong tree with the fuel system?

a) injector leak ?
b) fuel pump relay ? (what brand)
c) AMM resistance check out ?

Janspeed · 07-31-2021, 07:15 AM

d) throttle body axel wear? (causing intermittent vacume leak)

07-29-2021, 10:22 PM	#1
autoloclys Board Member Join Date: Dec 2016 Location: Boston MA	uneven running, fuel pressure issue? having an annoying issue but so far it hasnt left me stranded. In normal driving on the road, the engine in my '92 240 will occasionally stumble a little, its most noticeable between 1500-2000 rpm. Idle is smooth and above 2000 rpm the stumble is either not there or not noticeable both fuel pumps are new since i bought the car and seem to be running (i can hear them when i check), Fuel pressure regulator also seems fine, no fuel in the vacuum line. and all the fuel lines between the tank and the engine have been replaced, though the return line is hose and not hard pipe is it possible the intank or under car fuel pumps are running but not supplying sufficient pressure for certain conditions? neither one is a volvo part, but i would expect them to work or not work, rather than lose pressure slowly or intermittently. or am i totally up the wrong tree with the fuel system?

07-29-2021, 10:47 PM	#2
James M Bored member Join Date: May 2017 Location: Chico, CA	. Last edited by James M; 07-29-2021 at 11:22 PM..

07-31-2021, 07:15 AM	#5
Janspeed Board Member Join Date: Sep 2005	d) throttle body axel wear? (causing intermittent vacume leak) Last edited by Janspeed; 08-06-2021 at 04:25 PM..

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07-30-2021, 02:31 AM	#3
mattd1205 Board Member Join Date: Dec 2014 Location: Los Angeles, CA	I’d check for codes first if you haven’t already. If you suspect a fuel pressure issue, throw the autozone rental fuel pressure gauge on there. It doesn’t come with the fittings you need but you can cut up a fuel rail and part of the fuel line from a junk Volvo at the junkyard to make an adapter that will plumb into the tee fitting that comes with the gauge kit.