Loss of power when going over bumps

tempest · Jul 23rd, 2010, 14:05

Volvo 740 2.3 inj 1989 F reg B230E engine.

Intermittent problem with loss of power - engine splutters and tachometer suddenly drops revs to the point of almost stalling, but only under load when going over bumps. When this happens I push the clutch in and the engine revs ok. No problem starting and ticks over smoothly.

When the engine is cold there seems an almost imperceptible power loss under the same conditions until driven for a few miles and it then gets worse.

I have recently tried changing the air filter and the spark plugs to no avail. The fuel injection system is the mechanical type.

The key here seems to be the sudden movement when going over bumps on the road(no shortage of them!). I'm thinking fuel supply- maybe the in-tank fuel pump or electrical connections (the fuel gauge doesn't work properly so I keep the tank at least 3/4 full). Could be the main fuel pump not providing enough pressure (not sure where the pressure regulator is on the mechanical injection system). Fuel filter?

I had a problem with the fuel pump relay some years ago but a resolder solved that.

Any help would be appreciated.

CTCNetwork · Jul 23rd, 2010, 14:31

Hi,

Would be well worth checking your earth contacts in the engine bay especially those to the engine and in particular the alternator and starter earths.

Des. . .

tempest · Jul 23rd, 2010, 14:42

Thanks for that Des. I will go and check now.

tempest · Jul 23rd, 2010, 15:22

Hi Des

I've checked all the earths I can find back to the battery negative terminal and they are OK.

Going for the loose connection/component route sounds good to me.

The strange thing is that the engine revs fine even when the fault is occurring(with the clutch pushed in). If I release the clutch the fault continues. What I am not yet aware of is if the fuel pump noise changes in the the fault state. Being under pressure to drive at road speed prevents me form being able to be aware of everything which happens. Is their such a thing as a quiet road?

tempest · Jul 23rd, 2010, 19:24

I decided to have a look at the distributor cap and rotor and they seem ok but there is a connector and wiring, hall sensor? , which is refusing to go back into place. I presume it is meant to be held in place somehow by the distributor cap but it is in a place which is almost impossible to see.

I tried taking some images of the connector but even with a tiny camera it is not clear where it should go.

When I reconnected all the leads the car refused to start at all. I had marked all the leads to ensure they went back in the correct places and they are all pushed home firmly, and since I did not take the rotor arm off everything should have been as before (apart from the connector for the hall sensor).

I don't have the time to go through the spark test ATM but would this have anything to do with the hall sensor?

CTCNetwork · Jul 23rd, 2010, 20:24

Hi,

FAQ: Hall Sensor Info...

Should help.

The fuel pump is a possibility but a mere bump wouldn't, I think, deprive the engine of fuel to a point where it has an immediate effect. Certainly worth a check, even if to eliminate it from investigations...

Des. . .

RAW · Jul 27th, 2010, 22:51

Am I not right in sating that he fuel pumps in t etheae have two speeds. could it be that when going over bumps the pump is for some reason not running at the higher speed so the ending is starved if the necessary fuel to run unde load, but is still able to idle.

Richard

ps: on Reading this I've realised how silly it sounds and that it is somewhat unlikely! Oh well.

danielm85948 · Jul 28th, 2010, 02:43

Quote:

Originally Posted by tempest

Volvo 740 2.3 inj 1989 F reg B230E engine.

Intermittent problem with loss of power - engine splutters and tachometer suddenly drops revs to the point of almost stalling, but only under load when going over bumps. When this happens I push the clutch in and the engine revs ok. No problem starting and ticks over smoothly.

When the engine is cold there seems an almost imperceptible power loss under the same conditions until driven for a few miles and it then gets worse.

I have recently tried changing the air filter and the spark plugs to no avail. The fuel injection system is the mechanical type.

The key here seems to be the sudden movement when going over bumps on the road(no shortage of them!). I'm thinking fuel supply- maybe the in-tank fuel pump or electrical connections (the fuel gauge doesn't work properly so I keep the tank at least 3/4 full). Could be the main fuel pump not providing enough pressure (not sure where the pressure regulator is on the mechanical injection system). Fuel filter?

I had a problem with the fuel pump relay some years ago but a resolder solved that.

Any help would be appreciated.

change the fuel pump relay it is only £18 new

tempest · Jul 28th, 2010, 16:16

I managed to start the car but the idle was very erratic. I tried moving the hall sensor connector which is hanging loose and it appeared to change the idle state which suggested to me either a bad connection or a wire shorting intermittently.

Having looked through the forum archive and found a similar problem reported of losing power over bumps when a wire attached to the hall sensor shorts I decided to remove the distributor for access to the terminal connector.

Unfortunately the strain on the terminal wires was too much and 2 broke off.
Having a close look at the wiring it looks like the red (+) wire had lost some of its insulation and maybe was shorting. The black wire is still intact but the green wire broke at the crimp on the terminal.

I have ordered a new connector housing off Ebay.

The problem I have now is splicing some new wire onto the green/brown signal wire and the red power supply wire and attaching these to the terminals in a way which is solid, insulated and resists vibration.

I have considered either soldering the end of the old wire to new wire and using epoxy to "pot" the joint or maybe use some heatshrink insulation. The terminals are a different problem since they are crimp on types. It was easy enough to remove them even with the barb retainer on them, but opening up the crimp is difficult.

Any suggestions?

tempest · Aug 2nd, 2011, 22:52

Hi all, just to confirm I managed to replace the wiring in the distributor to the sensor and put it all back together.

Best I could do was solder the wires together as firmly as I could and insulate using electrical sleeving. The connector housing was delayed from Ebay so I decided to araldite the old connector in place.

Still working ok a year on.

Thanks for the help.

Jul 23rd, 2010, 14:05	#1
tempest New Member Last Online: May 14th, 2023 20:00 Join Date: Jul 2010 Location: Manchester	Loss of power when going over bumps Volvo 740 2.3 inj 1989 F reg B230E engine. Intermittent problem with loss of power - engine splutters and tachometer suddenly drops revs to the point of almost stalling, but only under load when going over bumps. When this happens I push the clutch in and the engine revs ok. No problem starting and ticks over smoothly. When the engine is cold there seems an almost imperceptible power loss under the same conditions until driven for a few miles and it then gets worse. I have recently tried changing the air filter and the spark plugs to no avail. The fuel injection system is the mechanical type. The key here seems to be the sudden movement when going over bumps on the road(no shortage of them!). I'm thinking fuel supply- maybe the in-tank fuel pump or electrical connections (the fuel gauge doesn't work properly so I keep the tank at least 3/4 full). Could be the main fuel pump not providing enough pressure (not sure where the pressure regulator is on the mechanical injection system). Fuel filter? I had a problem with the fuel pump relay some years ago but a resolder solved that. Any help would be appreciated.

Jul 23rd, 2010, 14:31	#2
CTCNetwork Forum Support Team Join Date: Dec 2004 Location: Liège, Belgium View Photos By: CTCNetwork	Hi, Would be well worth checking your earth contacts in the engine bay especially those to the engine and in particular the alternator and starter earths. Des. . . __________________ Density:- Not just a measurement ~ It's a whole way of Life.! ! ! I drive a Volvo, Please Don't Get In My Way! OldVolvos4Ever He shows up. People die. He vanishes. People should not be afraid of their governments. "He'll deliver more justice in a weekend than 10 years of your Governments should be afraid of their people... "V" courts & tribunals. Just stay out of his way." "I plan to."

Jul 23rd, 2010, 20:24	#6
CTCNetwork Forum Support Team Join Date: Dec 2004 Location: Liège, Belgium View Photos By: CTCNetwork	Hi, FAQ: Hall Sensor Info... Should help. The fuel pump is a possibility but a mere bump wouldn't, I think, deprive the engine of fuel to a point where it has an immediate effect. Certainly worth a check, even if to eliminate it from investigations... Des. . . __________________ Density:- Not just a measurement ~ It's a whole way of Life.! ! ! I drive a Volvo, Please Don't Get In My Way! OldVolvos4Ever He shows up. People die. He vanishes. People should not be afraid of their governments. "He'll deliver more justice in a weekend than 10 years of your Governments should be afraid of their people... "V" courts & tribunals. Just stay out of his way." "I plan to."

Jul 23rd, 2010, 14:42	#3
tempest New Member Last Online: May 14th, 2023 20:00 Join Date: Jul 2010 Location: Manchester	Thanks for that Des. I will go and check now.

Jul 23rd, 2010, 15:22	#4
tempest New Member Last Online: May 14th, 2023 20:00 Join Date: Jul 2010 Location: Manchester	Hi Des I've checked all the earths I can find back to the battery negative terminal and they are OK. Going for the loose connection/component route sounds good to me. The strange thing is that the engine revs fine even when the fault is occurring(with the clutch pushed in). If I release the clutch the fault continues. What I am not yet aware of is if the fuel pump noise changes in the the fault state. Being under pressure to drive at road speed prevents me form being able to be aware of everything which happens. Is their such a thing as a quiet road?

Jul 23rd, 2010, 19:24	#5
tempest New Member Last Online: May 14th, 2023 20:00 Join Date: Jul 2010 Location: Manchester	I decided to have a look at the distributor cap and rotor and they seem ok but there is a connector and wiring, hall sensor? , which is refusing to go back into place. I presume it is meant to be held in place somehow by the distributor cap but it is in a place which is almost impossible to see. I tried taking some images of the connector but even with a tiny camera it is not clear where it should go. When I reconnected all the leads the car refused to start at all. I had marked all the leads to ensure they went back in the correct places and they are all pushed home firmly, and since I did not take the rotor arm off everything should have been as before (apart from the connector for the hall sensor). I don't have the time to go through the spark test ATM but would this have anything to do with the hall sensor?

Jul 27th, 2010, 22:51	#7
RAW VOC Member Last Online: Feb 11th, 2024 10:42 Join Date: Nov 2007 Location: Nottingham	Am I not right in sating that he fuel pumps in t etheae have two speeds. could it be that when going over bumps the pump is for some reason not running at the higher speed so the ending is starved if the necessary fuel to run unde load, but is still able to idle. Richard ps: on Reading this I've realised how silly it sounds and that it is somewhat unlikely! Oh well.

Jul 28th, 2010, 16:16	#9
tempest New Member Last Online: May 14th, 2023 20:00 Join Date: Jul 2010 Location: Manchester	I managed to start the car but the idle was very erratic. I tried moving the hall sensor connector which is hanging loose and it appeared to change the idle state which suggested to me either a bad connection or a wire shorting intermittently. Having looked through the forum archive and found a similar problem reported of losing power over bumps when a wire attached to the hall sensor shorts I decided to remove the distributor for access to the terminal connector. Unfortunately the strain on the terminal wires was too much and 2 broke off. Having a close look at the wiring it looks like the red (+) wire had lost some of its insulation and maybe was shorting. The black wire is still intact but the green wire broke at the crimp on the terminal. I have ordered a new connector housing off Ebay. The problem I have now is splicing some new wire onto the green/brown signal wire and the red power supply wire and attaching these to the terminals in a way which is solid, insulated and resists vibration. I have considered either soldering the end of the old wire to new wire and using epoxy to "pot" the joint or maybe use some heatshrink insulation. The terminals are a different problem since they are crimp on types. It was easy enough to remove them even with the barb retainer on them, but opening up the crimp is difficult. Any suggestions?

Aug 2nd, 2011, 22:52	#10
tempest New Member Last Online: May 14th, 2023 20:00 Join Date: Jul 2010 Location: Manchester	Hi all, just to confirm I managed to replace the wiring in the distributor to the sensor and put it all back together. Best I could do was solder the wires together as firmly as I could and insulate using electrical sleeving. The connector housing was delayed from Ebay so I decided to araldite the old connector in place. Still working ok a year on. Thanks for the help.

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