My 1983 Volvo DL has been running very well in fact I just put new tires and a new radio in it. I was driving home from work-

-felt a slight shudder and 30 seconds later it died.

-it will start, run smoothly for 2 minutes and then surge, buck and stall.

-I replaced the Mass Air Sensor. Runs smooth now for 5 minutes then the RPMs surge then runs rough and then stalls.

HELP. The symptoms seemed Mass Air Flow Sensor failure but a new one did not help.

Thank you in advance

George
Arizona

 

fuel filter?

 

Changing the fuel filter. Unfortunately I broke the line going to the engine so I am awaiting a tool and tubing to repair the line.

 

Why did you replace the MAFS?
Your problem is definitely NOT the fuel filter.
Stop throwing your money away and diagnose the problem first!

 

Thank you Lev.

Other than reading and rereading troubleshooting advice I am a little out of my element even with a 30 year old fuel injection system.

I have attempted to see what scanner can be used but have not had much luck.

I had a MAF left over from a previous repair. The car acted initially like a failed MAF initially but in fact the car won't run even if I unplug the MAF.

If you have any concrete suggestions I am all eyes.

Thanks again

George

 

you need to determine if the surging/bucking/stalling is due to A) no spark or B) not enough fuel or C) too much fuel.

it could be some wiring is shorting or corroded and going high resistance when it gets hot.

it could be something like the hall sensor in the distributor is failing when it gets hot.

it could be a fuel pump problem (fuel pump relays, wiring, etc)

it could be the fuel pressure regulator that doesn't like being hot.

diagnose the root cause THEN replace the parts that need replacing, instead of randomly swapping things.

 

Changing a fuel filter helps establish a baseline for fuel system operation. It is a maintenance item and is not throwing money at anything.

 

Not so.
There is no reason to routinely change a FF besides enriching parts manufacturers--sure, it won't hurt anything but your wallet.
I only do it if there are symptoms such as fuel starvation under load. After 40 years in the car biz you learn a few things...
Whatever the wider discussion, certainly a FF would not cause Geosar's symptoms.

 

Well, that is a lot to absorb.

The fuel pressure is good.

It must be part of the EFI or electrical.

Onward.

Thanks for the interest.

George

 

New fuel filter.

I bypassed the fuel pump relay and have good fuel flow and pressure.

The car runs better, but runs unevenly. It idles irregularly and occasionally when I push the accelerator it misses and then stalls.

Took all of the ignition wires off, checked the connections and sprayed them with electronics spray.

Anything I might try?

Thank you.

 

hook up a old fashion timing light and see if its pulsing unevenly when the car stumbles/misses. if so, its an ignition problem. if not, its more likely to be a fuel problem.

 

Than you. Will do.

 

Check for vacuum leaks in lines and the big intake hose between the throttle body and the MAF. That hose can develop holes especially on the underside where it can contact the car body. Shoot carb cleaner at lines and hoses while the car is running. If Idle increases, there is a leak there. Some people use propane (not lit) to find leaks too.

I'd also unplug the in-tank pump while the engine is running to see if anything changes. But that's me.

 

check the wiring to the HALL sensor in the distributor. if that goes intermittent, all bets are off, engine bucking is not at all unexpected.

 

The timing light seemed to be solid right up until the engine stalls.

Fuel pump relay is good.

Fuel injectors check out electrically.

It still runs up and then stalls after about 3 minutes.

 

The timing light seemed to be solid right up until the engine stalls.

Fuel pump relay is good.

Fuel injectors check out electrically.

It still runs up and then stalls after about 3 minutes.

Not sure what the HALL is but will find out.

Disassembled the air intake hose along with the Air Mass Sensor. There was some oil in the hose. Cleaned it well and sprayed cleaner into the intake. Also sprayed cleaner into the fuel rail.



Thanks for all of the help.

George

 

the hall sensor is inside the distributor, and functionally somewhat equivalent to the 'points' of an old fashion ignition system. It provides the timing pulses to the ICU (Ignition Control Unit), which in turn triggers the power module to fire the coil. the ICU also provides cleaned up timing pulses to the ECU, which uses it to decide how much fuel to inject and when.

unluckily, I do not have the greenbooks wiring diagrams for 1983 240's, and I'm not quite sure which ignition system that used. I have 1975-1978, and 1984 on. hmm, in 1984, there was no separate power module, and only a very simple analog ICU.

I believe 83 was the first year for LH-II electronic fuel injection, but I've never been under the hood of anything older than 1987.

 

I have an ' 83 that would die on me for no apparent reason. It turned out that the wires to the main pump were taped together side by side and current was burning little pinholes through the insulation and shorting it out. Might check that, took me about 3 weeks to figure that one out.

 

Yes, that is on my list. The fuel pressure seems adequate.

I have made sure each fuel pump runs and they do.

Thank you for the help.

George

 

for LH injection, the fuel pressure has to be 42-44PSI above the manifold vacuum (so if there's -7 lbs vacuum, that would be 35-37 psi absolute).