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1975 B20 no start Kjet woes

Jack

Jack

junkman
Joined
Jul 7, 2011
Location
The Ass Cheek Of History
please help me before I lose my mind completely....problems started before I went parts cannon on this

1975 Volvo b20 with M40 original Kjet.
car came with a some random China fuel pump. I just installed a new fuel pump from VP thinking that may be it (china pump ran loud for months)

line pressure reads 4.6 (spec is between 4.6-5.3)
rest pressure is was about 30 psi (spec is min 24 max 51)

^That all seems normal

control pressure is where I found some issues, all but one WUR seemed bad
all WURs were setting the control pressure at 4.6 right away (max I believe is 3.7 aka 50-55psi)
one WUR started at 1.9 after I messed around with it (which seems to high) then after 3 min it does go to 3.7 as per test

PcavOVJ.jpg


car will every once in a while run for about 2 seconds then dies and sometimes with throttling it will run rough but as soon as you let go of throttle it dies

the other weird part is that sometimes the cold start injector will spray when starting and then most of the time it does not, when it does it sometimes seems to spray for few seconds and other times just very briefly

what does the plugged in sensor at the air flow meter do? the mechanism inside the air flow meter is mechanical, so what is this sensing? I also cant find any tests for it.
How do you test a thermal time switch?

We have ruled out:
fuel pump (replaced with brand new one)
fuel pump relay (tried multiple relays)
main relay (tried multiple relays)
fuel distributor (plunger checked, works smoothly; pressure test is correct)
cap and rotor (10k miles)
spark plugs (new)
spark wires (fairly new)
intake accordion (checked for holes, none)
starter (turns over fine)
ignition coil (spark is strong)
wiring from starter to cold start injector (continuity exists)

At this point it seems like we have two separate issues:
cold start injector mostly doesn't turn on upon crank
injectors do not inject fuel into engine unless gas pedal is depressed a lot or air flow sensor is manually held up (cannot maintain idle)

I need some help please
 
The sensor on the airflow sensor body is the ground used for sensing the plate is down so no airflow thus the fuel pumps can't run. It's a safety for when the engine stalls or you have an incident. To test fuel pump function you can disconnect the sensor and that will make the fuel pumps run with key on.

That control pressure seems like it's a bit low on startup but rises to another slightly low figure. When the control pressure is the same as system it's clogged and will lean out the engine.

The thermal time switch controls how long the injector fires so the hotter the engine the less time it should fire the injector until when fully hot there should be no spray. But a cold engine should get a good spritz from the injector. They can drip fuel when they fail.
 
makes sense about the airflow sensor.

That control pressure seems like it's a bit low on startup but rises to another slightly low figure.

why do you say that?
it was like 57F today and according to chart above, control pressure should have started at around 1.4 or so but it started at 1.9 then it rose to 3.7 \
and 3.7 is where it should be at after 3 min

When the control pressure is the same as system it's clogged and will lean out the engine.

thats how we ruled out the other WURs because they were full pressure right away... aka super lean

The thermal time switch controls how long the injector fires so the hotter the engine the less time it should fire the injector until when fully hot there should be no spray. But a cold engine should get a good spritz from the injector. They can drip fuel when they fail.

Thank you I undertsand the operation. The engine never got to operating temp. Book says depending on temp, cold start can run up to 12sec..
does not drip.
is there a test for thermal time switch
 
Last edited:
Ok I thought that 1.9 bar seemed a bit low for a warmed up engine. I was mistaken. For easier starting do you have the full 12v at the coil and then after startup it uses the ballast resistor?
 
Some thoughts, apologize if any of these are remedial or something you have tried already:

1) Have you checked each injector is working properly? When I picked up my 1975 242 from Luke almost 10 years ago, it initially ran fine then lapsed into having hard starts. It was running similar to yours, on cold start up would need to feather the throttle to keep it going, and after several minutes it would smooth out. My thought it was running on one cylinder and as it warmed up the others would come on line. It would take 5-7 minutes for the car to be driveable. I didn't take any pressure readings, I more assumed it was an issue with the control pressure regulator. Talk about this in my old project build postings (https://turbobricks.com/index.php?t...h2-4-upgrade-image-heavy.324743/#post-5455589) Have you been able to keep the car running for several minutes to see if anything changes when the engine warms up? The quick and dirty test of the fuel pump is if it could fill a beer bottle in under 10 seconds.

14842112537_47141595f1_b.jpg


2) Have you checked the temp sensors? Had one go bad in my 1973 142 (d-jet) and that cause all sorts of running/idling issues.

3) Have you checked each cylinder with a timing light to make sure the electrons are going all of the way to the spark plugs? This was an issue after installing the 1990 B230F into the 242. The engine came from a car which sat for about 10 years (82K miles, owner died and took a while for the spouse to sell it) It had running issues and the check engine light would get triggered. Had a set of Bougicords on it which were the source of the ignition issue.

4) Looks like your fuel pressure numbers are good, have you checked your in-tank pump at all?

14932509956_608540c4b1_b.jpg



I have all of the 1975 B20 engine wiring harness, fuel distributor, etc in a box from the B230 swap, if you need anything from there, then PM me.
 
polaris said:
4) Looks like your fuel pressure numbers are good, have you checked your in-tank pump at all?
Click to expand...
Pre-78 don't have an in-tank pump as standard (unless they've had a replacement tank fitted).

The old pre-78 tanks did have problems with the internal feed pipes getting rust holes, but that's not a problem here since there's good line pressures.

Guess you've already seen this 140 engine Green Book from https://ozvolvo.org/archive/archive.php ?

TP10867-1_1974_140_section_2_engine.pdf
 
bgpzfm142 said:
Pre-78 don't have an in-tank pump as standard (unless they've had a replacement tank fitted).

The old pre-78 tanks did have problems with the internal feed pipes getting rust holes, but that's not a problem here since there's good line pressures.
Click to expand...
FYI: In the US there was a government recall for the gas tanks in the 1975 240s. Depending on when this was done, the car may be fitted with the later style 240 tank with the in-tank pump set up. That is the case with my 1975 242.
https://www.turbobricks.com/index.php?threads/help-identifying-recall-fuel-tank-in-75-240.292445/
 
On the non transfer pump gas tanks there was a sock filter on the pickup tube. This has a tendency to clog which happened on our 74 142 long ago. You can access the filter from removing the drain plug in the tank.
 
polaris said:
Some thoughts, apologize if any of these are remedial or something you have tried already:



14842112537_47141595f1_b.jpg


2) Have you checked the temp sensors? Had one go bad in my 1973 142 (d-jet) and that cause all sorts of running/idling issues.

3) Have you checked each cylinder with a timing light to make sure the electrons are going all of the way to the spark plugs? This was an issue after installing the 1990 B230F into the 242. The engine came from a car which sat for about 10 years (82K miles, owner died and took a while for the spouse to sell it) It had running issues and the check engine light would get triggered. Had a set of Bougicords on it which were the source of the ignition issue.

4) Looks like your fuel pressure numbers are good, have you checked your in-tank pump at all?

14932509956_608540c4b1_b.jpg



I have all of the 1975 B20 engine wiring harness, fuel distributor, etc in a box from the B230 swap, if you need anything from there, then PM me.
Click to expand...

1) Have you checked each injector is working properly? When I picked up my 1975 242 from Luke almost 10 years ago, it initially ran fine then lapsed into having hard starts. It was running similar to yours, on cold start up would need to feather the throttle to keep it going, and after several minutes it would smooth out. My thought it was running on one cylinder and as it warmed up the others would come on line. It would take 5-7 minutes for the car to be driveable. I didn't take any pressure readings, I more assumed it was an issue with the control pressure regulator. Talk about this in my old project build postings (https://turbobricks.com/index.php?t...h2-4-upgrade-image-heavy.324743/#post-5455589) Have you been able to keep the car running for several minutes to see if anything changes when the engine warms up? The quick and dirty test of the fuel pump is if it could fill a beer bottle in under 10 seconds.

No, I still need to check each injector and see whats up. Theres no fuel coming out of 1 when engine cranks.
I cant keep that car on longer then few seconds. This happened all of a sudden, Car ran "great" for the last 15k? miles since we have owned it


2) Have you checked the temp sensors? Had one go bad in my 1973 142 (d-jet) and that cause all sorts of running/idling issues.

I was trying to check the thermo switch sensor but I dont see specs for it. The WUR that we currently have on seems to be working if pressure readings are correct

3) Have you checked each cylinder with a timing light to make sure the electrons are going all of the way to the spark plugs? This was an issue after installing the 1990 B230F into the 242. The engine came from a car which sat for about 10 years (82K miles, owner died and took a while for the spouse to sell it) It had running issues and the check engine light would get triggered. Had a set of Bougicords on it which were the source of the ignition issue.
No, not each cylinder and I need to recheck the ignition system again

4) Looks like your fuel pressure numbers are good, have you checked your in-tank pump at all?
as others mention below, there is no in tank pump originally... but I did install a new tank with a riser pump... I did check that

have all of the 1975 B20 engine wiring harness, fuel distributor, etc in a box from the B230 swap, if you need anything from there, then PM me.
Click to expand...
good to know as I might need some stuff. Thank you
 
Did you recently change the fuel filter? I've had a kjet system clog after fuel filter change. The filter hadn't been done in many years and just disturbing the system with a new filter sent crud into the injectors.
 
dl242gt said:
Did you recently change the fuel filter? I've had a kjet system clog after fuel filter change. The filter hadn't been done in many years and just disturbing the system with a new filter sent crud into the injectors.
Click to expand...
No filter is good, two years maybe
I would think fuel pressure readings would be off


Raining today m, hopefully I’ll solve this this weekend
 
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