Engine won't rev and hunts

[ANDTWENTY]

Originally Posted by mocambique-amazone

Most of suppliers won't take back electrical parts if they are out of the wrapping, for good reason.
You have to prove the part is faulty by process while the production....

Good luck, Kay

There seem to be a few different in tank ones so thought if I ordered the wrong one I could send it back, without using it so still in wrapper

[ANDTWENTY]

Originally Posted by mocambique-amazone

OK, let's start

A 1990 940 is a LH2.4 or a diesel

There will be no port for the fuel pressure

This model is with cold start injector

With two fuel pumps

With catalyst

With a ....016 MAF ( AMM)

There is only one variation possible: Regina = mostly found in the great (past) Staates
Regina is crap in my opinion

Not sure what the Regina is?

I don't know the history of this car, especially if "qualified" people did work on.
To be clear: "not qualified" you will find even at a pro-workshop, even at a volvo dealer workshop
I did solve a looooooot of hughe and unbelievable faults done by "pros"

If there is no code at the diode inside the engine bay and no warning light at the dashboard I would say the AMM is the faulty part.
Don't try to clean this. The LH2.4 does clean them by there own by heating them up and burn the stuff on the wire away.

Cap and rotor : only made by Bosch, nothing else I use
All sensors : the same, Bosch and really nothing else. I would prefer even a used Bosch one than a new s... made by all others, sorry.

If you follow the instructions about the diagnostic box in the engine bay you will be able to do a diagnose of the TPS and other stuff too.
Most people know the fault codes only.

Good luck, Kay

I keep meaning to use the fault code reader to test the sensors just never got round to it but I'll try that when I get in from work and see what it says.

The cap and rotor and new Bosch ones and all the sensors seem to be original Bosch ones too, just don't like the idea of how much they cost!!

Is there a way to test the sensor incase the code reader doesn't give anything back? Just so I can be sure!?
Thanks for the good information though!

[Laird Scooby]

Originally Posted by mocambique-amazone

The lift pump is really only a lift pump. No pressure needed.
The fuel line between the tank and the pump under the car isn't made for high pressure

My data's aren't on my mobile. I will have a closer look at Monday evening earliest.

Have a nice weekend, Kay


I would swap a known working AMM first

Kay, that ebay one only flows a maximum of 1.25L/min or 75L/hr. While i agree that it is only a lift pump so pressure isn't the paramount consideration, the flow MUST be considered.

Originally Posted by ANDTWENTY

Thank you for this, so ruffly speaking then would you say that one I found is what you'd expect output wise? Presumably if it's low pressure then pinching the line may not be conclusive enough? Is there another way to test the pump without taking it all out the tank?

Is there a way to test the AMM as getting hold of a new one is expensive and second hand ones seem hard to come by

Nowhere near a high enough flow output, it needs to flow at least what the underbody pressure pump is capable of flowing or it will cause cavitation (in simple terms, trying to pump air pockets) in the pressure pump which will destroy the pressure pump.
Check the flow on this pressure pump :

https://www.rockauto.com/en/moreinfo...1433970&jsn=15

As you'll see, the maximum flow is 40 Gall/hr so the lift pump in the tank needs to flow at least this amount. Therefore 15 gall/hr (aka 75L/hr) is NOT enough.

Originally Posted by ANDTWENTY

There seem to be a few different in tank ones so thought if I ordered the wrong one I could send it back, without using it so still in wrapper

If it is unused, in the packaging, almost everywhere will accept returns.

Also, even 4.5psi will be enough to make that fuel line hard to squash with finger and thumb.

I'm not saying thre isn't a problem with the MAF but if you don't have enough flow from the in-tank pump, it won't rev properly. Have you tried bringing the revs up slowly and gently rather than opening the throttle wide in one go? If you can bring the revs up this way, it suggests the fault is lack of flow/pressure rather than the MAF, especially as the idle went rough when you unplugged the MAF previously.

[Laird Scooby]

Originally Posted by ANDTWENTY

The cap and rotor and new Bosch ones and all the sensors seem to be original Bosch ones too, just don't like the idea of how much they cost!!

That's the price you pay for sharing them with a Porsche! Lucky for you it's the 924 and a couple of others so they're semi-affordable!

My dizzy cap and rotor are shared with 6 cylinder BMWs and no others so are ridiculously expensive, as for the Fuel Pressure Regulator on mine, shared with the 911 and a couple of other now mainly obsolete cars, mostly in the UK i was quoted £3-500 because of that!

[ANDTWENTY]

Do we know the specs of the original in tank fuel pump? I can't seem to find one online that is definitely original? Surely that way we can look up the flow and pressure and match one?

It definitely says online that the in tank one is low pressure but it would make sense for it to be the same volume output as the high pressure pump to avoid the cavitation, but then again provided the suction is within the fuel tank would it not be able to draw it out of the tank?

I might just whip it out l, check for a part number and also check it doesn't work by hooking it up to 12volt.

In respect to the revving I have tried opening the throttle both slow and fast, it doesn't seem to make much difference, I can't remember if there's any slight difference but from what I remember there isnt. It's as though as soon as the TPS is signalling open throttle it just goes bad, it tends to hunt the engine though it revs up and down a bit. I can check when I'm at home but I'm working now. Is it possible to upload a video here?

When I disconnected the MAF sensor it did make a difference to the idle which leads me to believe it may work but perhaps not properly!? However if this pump is not working it may be best to fix that and then try the MAF sensor?

[Laird Scooby]

Originally Posted by ANDTWENTY

Do we know the specs of the original in tank fuel pump? I can't seem to find one online that is definitely original? Surely that way we can look up the flow and pressure and match one?

It definitely says online that the in tank one is low pressure but it would make sense for it to be the same volume output as the high pressure pump to avoid the cavitation, but then again provided the suction is within the fuel tank would it not be able to draw it out of the tank?

I might just whip it out l, check for a part number and also check it doesn't work by hooking it up to 12volt.

In respect to the revving I have tried opening the throttle both slow and fast, it doesn't seem to make much difference, I can't remember if there's any slight difference but from what I remember there isnt. It's as though as soon as the TPS is signalling open throttle it just goes bad, it tends to hunt the engine though it revs up and down a bit. I can check when I'm at home but I'm working now. Is it possible to upload a video here?

When I disconnected the MAF sensor it did make a difference to the idle which leads me to believe it may work but perhaps not properly!? However if this pump is not working it may be best to fix that and then try the MAF sensor?

I did all the specs a few months back when i had to renew my in-tank pump. I can't remember them all now and can't find them online because it was a long, torturous route to find them (Bosch no longer make the original as far as i could work out at the time) and the Valeo one is NOT up to the job on an injection car, simply hasn't got the flow.

The underbody pump isn't capable of drawing a vacuum to pull the fuel through (hence the need for the in-tank pump) so will not pull extra fuel through a pump that can only supply 1.25L/minute.

It might say online it's the in-tank pump (the Valeo one) but don't forget there were also carburettor 740s and (i'm not sure) i think there were a few 940 carbs. Trouble is with sellers, they don't always know (or care about) the correct spec, it took me several days of more or less continual searching to find the original spec.

The original Volvo part number is 3507436, if you look through this pdf on Pg20 (by DOcument Viewer Pg number) you will see the part numbers for the "Pre-pump" and cross referencing that to Rock Auto and others comes up with a pump that matches the spec i've already given.

http://www.myvolvolibrary.info/Tech_...DataPocket.pdf

Bookmark that pdf - you'll need it at some point in the future!

As for "just whip it out" - good luck with that! Refer to my pics above, that plstic ring is tight with a capital "F" and needs to go back the same way (i use a piece of wood and a lump hammer to knock the wood, Volvo have a special spanner), once out and the various hoses are disconnected (again, easier said than done!) you pull backwards and slightly upwards on the sender plate. Then you turn it 90 degrees (can't remember if it's left or right and then start pulling the plate towards the back of the car. As the pump and sender start to come out, if you turned the plate 90 degrees to the left when you first turned it, you need to move the plate to the right and draw the pump/sender unit out in a curved motion. Opposite way round if you turned the plate to the right to start after bringing it slightly backwards. THen if you're lucky, you can lift the sender/pump assembly out through the access hole and see the pump. Note how the wires go onto it, 8mm socket if memory serves. Also the strange clip at the bottom that secures the sender to the pump.
YOu'll probably find the strainer is collapsed on the bottom or at least blocked.

Make sure you don't drop the sealing ring in the tank!!!!!

Refitting - you "Haynes it" - refitting is the reverse of removal.

I used some silicone grease on the seal and also the plastic lock ring threads to aid refitting and getting it tight. I also found after about two months i needed to check-tighten it with the wood and hammer as it settled and leaked a little.

Going totally off-topic, just for Kay, how to convert a speedo that expects pulses from a diff with a 96 tooth reluctor ring (1988 models with ABS) to read correctly on a 48 tooth diff :


Before ^^^^^


After ^^^^^

A bit brutal but SMD has never been my thing, even 30 years ago and time and other things mean my paws are no longer steady enough so i had to blob the solder on instead. It's linking pins 9, 10 and 11 on that chip, 10 is N/C so doesn't matter but pin 9 is the Q3 output from a binary ripple counter chip and pin 11 is Q2 output, in other words, Q3 = divide by 8 and Q2 = divide by 4 (2 to the power of 3 and 2 respectively) so the same technique could be used to fit a 48 tooth axle to an originally 12 tooth axled car in theory.
Just the ABS ECU to convert now! That's still expecting 96 pulses per turn as well!

Sorry for going off-topic but i remember Kay said in one of my threads about not being able to do it, just wanted to show it is possible!

*** EDIT *** Nearly forgot, you can upload a video to YouTube then copy the "Share" link from there into you post as a link.

If you want to upload photos, use a photo hosting site such as postimages.org and select the "Hotlink for forums" by clicking the blue button at the end of the link then paste that where you want the photo to appear in your post.
Other photo hosting sites are available, i use postimages as it's free and easy to use - it has to be as software is not my strong point!

[mocambique-amazone]

Thank you about the info of the ABS / Speedo reading Dave.
New to me. I will store this.


The engine won't notice a lift pump not working if the tank is at minimum half full.
Lower than this the main pump will produce a vacuum and bubbles are in the fuel.

If your car has the same problem with the tank full you save time and money for the lift pump later

Good night, Kay

[ANDTWENTY]

Originally Posted by Laird Scooby

I did all the specs a few months back when i had to renew my in-tank pump. I can't remember them all now and can't find them online because it was a long, torturous route to find them (Bosch no longer make the original as far as i could work out at the time) and the Valeo one is NOT up to the job on an injection car, simply hasn't got the flow.

That makes sense as to why I can't find much from searching around on the internet, I can find post 94 ones for the newer 940's which I was wondering if they would work, the only thing I can tell is different from a quick look is that it has a plug connector rather than nuts for the wires but will look at flows and pressure perhaps.

Originally Posted by Laird Scooby

The underbody pump isn't capable of drawing a vacuum to pull the fuel through (hence the need for the in-tank pump) so will not pull extra fuel through a pump that can only supply 1.25L/minute.

It might say online it's the in-tank pump (the Valeo one) but don't forget there were also carburettor 740s and (i'm not sure) i think there were a few 940 carbs. Trouble is with sellers, they don't always know (or care about) the correct spec, it took me several days of more or less continual searching to find the original spec.

The original Volvo part number is 3507436, if you look through this pdf on Pg20 (by DOcument Viewer Pg number) you will see the part numbers for the "Pre-pump" and cross referencing that to Rock Auto and others comes up with a pump that matches the spec i've already given.

http://www.myvolvolibrary.info/Tech_...DataPocket.pdf

Bookmark that pdf - you'll need it at some point in the future!

It may be then that I have to order the one from America, I just rather get one from England as it would be quicker and if it was wrong could always send it back but its looking like this is my only option! thanks for that document too!

Originally Posted by Laird Scooby

As for "just whip it out" - good luck with that! Refer to my pics above, that plstic ring is tight with a capital "F" and needs to go back the same way (i use a piece of wood and a lump hammer to knock the wood, Volvo have a special spanner), once out and the various hoses are disconnected (again, easier said than done!) you pull backwards and slightly upwards on the sender plate. Then you turn it 90 degrees (can't remember if it's left or right and then start pulling the plate towards the back of the car. As the pump and sender start to come out, if you turned the plate 90 degrees to the left when you first turned it, you need to move the plate to the right and draw the pump/sender unit out in a curved motion. Opposite way round if you turned the plate to the right to start after bringing it slightly backwards. THen if you're lucky, you can lift the sender/pump assembly out through the access hole and see the pump. Note how the wires go onto it, 8mm socket if memory serves. Also the strange clip at the bottom that secures the sender to the pump.
YOu'll probably find the strainer is collapsed on the bottom or at least blocked.

Make sure you don't drop the sealing ring in the tank!!!!!

Refitting - you "Haynes it" - refitting is the reverse of removal.

I used some silicone grease on the seal and also the plastic lock ring threads to aid refitting and getting it tight. I also found after about two months i needed to check-tighten it with the wood and hammer as it settled and leaked a little.

I saw a video on youtube of someone that removes it and he made it look easy! haha just thought I would get it out as I'm going to anyway, that way I could check for part numbers and see what it looks like to match it to a new one and double check it has gone. Might try filling the tank up and see if the problem eases or goes with more fuel to help pin point this as an issue first.

Originally Posted by mocambique-amazone

The engine won't notice a lift pump not working if the tank is at minimum half full.
Lower than this the main pump will produce a vacuum and bubbles are in the fuel.

I will try this in the morning and see if the problem improves, this way I should know for sure if its the pump.

Originally Posted by mocambique-amazone

If your car has the same problem with the tank full you save time and money for the lift pump later

do you mean because I can run the tank above half way and not pay for the pump haha

[Laird Scooby]

Originally Posted by ANDTWENTY

That makes sense as to why I can't find much from searching around on the internet, I can find post 94 ones for the newer 940's which I was wondering if they would work, the only thing I can tell is different from a quick look is that it has a plug connector rather than nuts for the wires but will look at flows and pressure perhaps.

Not as simple as that! The Mk2 940s had a single pump only so will give too much pressure into the underbody pump.


It may be then that I have to order the one from America, I just rather get one from England as it would be quicker and if it was wrong could always send it back but its looking like this is my only option! thanks for that document too!

You're welcome on the document, another member needed an in-tank pump for a 940, eventually got one from Volvo for £OUCH and it took about two weeks to arrive if memory serves - Rock Auto is just as quick!



I saw a video on youtube of someone that removes it and he made it look easy! haha just thought I would get it out as I'm going to anyway, that way I could check for part numbers and see what it looks like to match it to a new one and double check it has gone. Might try filling the tank up and see if the problem eases or goes with more fuel to help pin point this as an issue first.


It's easy when you've done it a few times - not so when you first try! Also if you do fill the tank and it doesn't run, you've got to be able to empty that extra fuel out to do the job so you're not breathing a lot of petrol fumes while you change the pimp. It's not nice!
Given this appears to have happened suddenly, i'd say the pump gave up the ghost suddenly.





I will try this in the morning and see if the problem improves, this way I should know for sure if its the pump.

do you mean because I can run the tank above half way and not pay for the pump haha

Not a wise move as it puts undue stress on the main pump. Previous owner of mine did that, i was lucky in that the underbody pump was good enough to keep the thing going when the level dropped but eventually those were the clues that the in-tank pump was FUBAR - it would cut out for no apparent reason, difficult starting, would idle but not rev, not even bringing the revs up slowly/gently. That was why i fitted the NRV as a test, to see if it was dropping pressure back to the tank when it shouldn't. That further exposed the in-tank pump as the culprit.

[ANDTWENTY]

I bought the car with the issue so I'm not 100% sure how suddenly it happened, the previous owner didn't use the car in the last 2 years as he lost his leg, he had it serviced for the last year before he passed away and I think it was his gardener that occasionally started the car but I'm not sure at what point the issue arose.

I just saw that the newer pumps are a much higher pressure so thats out the window haha, this is proving to be a bit of a nightmare! I have a friend that works at Volvo so in the slight off chance I asked if he could track anything down.

Originally Posted by Laird Scooby

Not a wise move as it puts undue stress on the main pump. Previous owner of mine did that, i was lucky in that the underbody pump was good enough to keep the thing going when the level dropped but eventually those were the clues that the in-tank pump was FUBAR - it would cut out for no apparent reason, difficult starting, would idle but not rev, not even bringing the revs up slowly/gently. That was why i fitted the NRV as a test, to see if it was dropping pressure back to the tank when it shouldn't. That further exposed the in-tank pump as the culprit.

Yea obviously wouldn't me a solution but would be enough to know if this is the issue or not for now, the plan is to get the car mot'd, tax and insured for October 1st so I can sort my current one and not waste money on tax if you know what I mean so Its not as though I need the car urgently. just wanted to get it sorted, hate waiting around for parts haha, and if this doesn't fix it then I have time to sort it haha