Fuel System: 140 Carb: - Losing power under load

Computer Jones · Sep 17th, 2012, 18:25

Hello everyone, first post here. I recently bought a '73 144 Deluxe (B20A, single Stromberg carb) and I've had an intermittent problem with the engine shuddering or completely losing power under load (i.e. above 50mph; it doesn't seem to happen when revving in neutral). It's always able to idle, and doesn't stall. At times I've been able to drive for hours on the motorway with no problems, which is a bit confusing.

I have a feeling it's a problem with the fuel system- the car sat for 20 years and no doubt there's some crud in the tank and fuel lines. I'll start by checking the fuel filter, but I just thought I'd see if anyone else has had the same problem, or any suggestions. I also just wanted to say hi!

Oh, also: the old fuel was drained from the tank by the previous owner, but I don't know if he actually cleaned it out properly. I'm also suspicious that the fuel pump is the culprit (clogged up, or just worn out).

Here's a picture of the car, for good measure.

Clan · Sep 17th, 2012, 18:46

yes fuel pump seems most likely , but also check carburettor diaphragm in the top of the carb ..

Computer Jones · Sep 18th, 2012, 00:28

Thanks, I heard the carb diaphragm is prone to failure. I'll check that out too!

Derek UK · Sep 18th, 2012, 12:08

+1 for the diapragm.

Computer Jones · Sep 22nd, 2012, 18:37

Diaphragm seems to be in good shape, as far as I can tell. I might buy a replacement if only because it's good to have a spare.

I couldn't see an obvious fuel filter on the carb, unless it's hidden inside somewhere. Time to check that Haynes manual again...

Derek UK · Sep 23rd, 2012, 16:34

Fuel filter normally a see through type between the pump and the car. Best nearer the pump. Not originally fitted by Volvo who relied on a filter in the pump. The original ones had a lid with a screw that could be removed to clean the filter screen.
Tank may still be dirty. Also try blowing back through to the tank. A bit of extra tube should allow you to blow back through by mouth. Not the best job but it gives you a better idea as to whether it's blocked up than giving it a blast with an air line. Water in the system also a problem sometimes.
Diapragm can look OK but have small cracks or just be stretched and baggy. A new one is cheap and worth fitting regardless. Check that your points are correctly set and that the advance retard is working. Rotor should snap back after a slight turn to the max stop.
Lots of variables.................

stigansven · Feb 4th, 2013, 21:38

Do the diaphragm it's a must, then put a Clear filter "before" the pump. If the pump is a AC just clean the filter if it's a Pierburg bin it because you will find that parts are hard to come by. You can still buy a QH pump NEW I have just bought one three days ago as a spare.
A TIP, place a speaker magnet on the bottom of your tank away from the outlet, in the middle trying not to foul the sender unit yet near enough to the sender inlet. I then drained mine and Hoovered up the crud in the middle. It took three atemps but it worked for me.
Stigansven

Computer Jones · Feb 4th, 2013, 22:32

I was thinking a filter before the pump would be a good idea. I forget which sort of pump it was; neither AC nor Pierburg. I replaced it with a new one- 30 euro from Scandix...

good idea on the fuel tank cleaning, but I might be alright now.

Sep 17th, 2012, 18:25	#1
Computer Jones Junior Member Last Online: Feb 28th, 2021 13:40 Join Date: Sep 2012 Location: Oxford	Losing power under load Hello everyone, first post here. I recently bought a '73 144 Deluxe (B20A, single Stromberg carb) and I've had an intermittent problem with the engine shuddering or completely losing power under load (i.e. above 50mph; it doesn't seem to happen when revving in neutral). It's always able to idle, and doesn't stall. At times I've been able to drive for hours on the motorway with no problems, which is a bit confusing. I have a feeling it's a problem with the fuel system- the car sat for 20 years and no doubt there's some crud in the tank and fuel lines. I'll start by checking the fuel filter, but I just thought I'd see if anyone else has had the same problem, or any suggestions. I also just wanted to say hi! Oh, also: the old fuel was drained from the tank by the previous owner, but I don't know if he actually cleaned it out properly. I'm also suspicious that the fuel pump is the culprit (clogged up, or just worn out). Here's a picture of the car, for good measure. Last edited by Computer Jones; Sep 17th, 2012 at 18:35.

Sep 17th, 2012, 18:46	#2
Clan Experienced Member Last Online: Today 08:35 Join Date: Jun 2007 Location: L/H side	yes fuel pump seems most likely , but also check carburettor diaphragm in the top of the carb .. __________________ My comments are only based on my opinions and vast experience .

Sep 18th, 2012, 00:28	#3
Computer Jones Junior Member Last Online: Feb 28th, 2021 13:40 Join Date: Sep 2012 Location: Oxford	Thanks, I heard the carb diaphragm is prone to failure. I'll check that out too!

Sep 18th, 2012, 12:08	#4
Derek UK VOC Member Last Online: Today 14:22 Join Date: Jul 2006 Location: Chatham	+1 for the diapragm.

Sep 22nd, 2012, 18:37	#5
Computer Jones Junior Member Last Online: Feb 28th, 2021 13:40 Join Date: Sep 2012 Location: Oxford	Diaphragm seems to be in good shape, as far as I can tell. I might buy a replacement if only because it's good to have a spare. I couldn't see an obvious fuel filter on the carb, unless it's hidden inside somewhere. Time to check that Haynes manual again...

Sep 23rd, 2012, 16:34	#6
Derek UK VOC Member Last Online: Today 14:22 Join Date: Jul 2006 Location: Chatham	Fuel filter normally a see through type between the pump and the car. Best nearer the pump. Not originally fitted by Volvo who relied on a filter in the pump. The original ones had a lid with a screw that could be removed to clean the filter screen. Tank may still be dirty. Also try blowing back through to the tank. A bit of extra tube should allow you to blow back through by mouth. Not the best job but it gives you a better idea as to whether it's blocked up than giving it a blast with an air line. Water in the system also a problem sometimes. Diapragm can look OK but have small cracks or just be stretched and baggy. A new one is cheap and worth fitting regardless. Check that your points are correctly set and that the advance retard is working. Rotor should snap back after a slight turn to the max stop. Lots of variables.................

Feb 4th, 2013, 21:38	#7
stigansven I've Been Banned Last Online: Nov 10th, 2013 22:01 Join Date: Dec 2005 Location: OLDHAM Lancs	Do the diaphragm it's a must, then put a Clear filter "before" the pump. If the pump is a AC just clean the filter if it's a Pierburg bin it because you will find that parts are hard to come by. You can still buy a QH pump NEW I have just bought one three days ago as a spare. A TIP, place a speaker magnet on the bottom of your tank away from the outlet, in the middle trying not to foul the sender unit yet near enough to the sender inlet. I then drained mine and Hoovered up the crud in the middle. It took three atemps but it worked for me. Stigansven

Feb 4th, 2013, 22:32	#8
Computer Jones Junior Member Last Online: Feb 28th, 2021 13:40 Join Date: Sep 2012 Location: Oxford	I was thinking a filter before the pump would be a good idea. I forget which sort of pump it was; neither AC nor Pierburg. I replaced it with a new one- 30 euro from Scandix... good idea on the fuel tank cleaning, but I might be alright now.

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