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240 '85 B230F fuel cut in 1st gear

"At full throttle, manifold pressure is close to barometric, so the fuel pressure gauge reads about 2.5 bar (36 psi). At idle, absolute pressure in the manifold is about 0.3 bar (0.7 bar less than barometric). Now the manifold absolute pressure pushing the pressure regulator diaphragm is only 0.3 bar instead of 1 bar. The reduced manifold pressure on the diaphragm allows it to move away from the opening, returning more fuel to the tank, and dropping the gauge fuel pressure in the distributor pipe to about 1.8 bar (2.8 absolute). The relative pressure at the injector tip is still 2.5 bar (2.8 minus 0.3 absolute). That's why fuel delivery per injector is not affected by changes in the manifold absolute pressure."


1.8 bar = 26.1 psi
 
lunchb0x said:
tachometer will immediately jump to ~1200 RPM ... I can press the gas pedal all I want but the car doesn't respond until the RPM gets down to normal idle and then the car snaps back and drives just fine..I noticed yesterday the car feels as if its lurching when I'm cruising around in higher RPMs while the A/C is on.
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Tach Test - Remove wires going to positive side of coil and tape them so they don't ground out, and hook a direct wire from the battery to this coil's post. Each vehicle requires a coil designed for that EFI (ignition side)...check coil's number and see if its for LH 2.2...might ohm spec it also.

Temp Sensor - I'd ohm check it....Volvo had two different temp sensors for EFI side...1984s is different from LH 2.4...don't know which sensor LH 2.2 used When I get a vehicle, that's the first thing that gets replaced. Generally, they tell EFI engine is colder than it is when they fail, which is not what you have reported (like a lean mixture).

Timing, throttle plate, and idle RPM must be set to OEM's spec...as they explain how to do it.
 
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Correction Made - "Tach Test - Remove wire(s) going to positive side of coil and tape them so they don't ground out, and hook a direct wire from the battery to this coil's post."
 
84B23F said:
Correction Made - "Tach Test - Remove wire(s) going to positive side of coil and tape them so they don't ground out, and hook a direct wire from the battery to this coil's post."
Click to expand...

I will test this when I get a chance. The tach issue has been pretty intermittent and I haven't seen it in a while.


I pulled and stripped the wiring harness back to the firewall and replaced/repaired a couple wires. The wire for the cluster temp sensor and wire for the oil pressure sensor were degraded inside the harness. I also replaced the coolant temp sensor for the ECU with a bosch oem replacement as it was cheap.

So before doing all this I screwed up and applied power to the ground wire (blue/white) for the IAC when trying to adjust the MAF with the LED tool. I absentmindedly pulled into the wrong wire and I think I fried the IAC as the car died when I did so and would start and idle at like ~200rpm. I picked up an IAC from PnP from a LH 2.2 240.

When I got the car back together with the replacement IAC the car idled at ~1500 rpm. I gave the IAC a few delicate love taps and the idle dropped down where it should be. I had cleaned it with some carb cleaner but it might of still been a little sticky. After driving it around a bit Sunday the car is idling where it should and seems to run fine besides the cutout.

I noticed that when the IAC is unplugged the car does not cut out like it has been. With the IAC plugged back in the car cuts out on first start when rev'd to ~1900 rpm. Still only cutting out once and only after the car is started, does not happen again while running.

When I inspected the harness I did not see any other wires with degraded shielding or breaks. I've also swapped ECU's and ICU's previously and the cut out persists. Is there any other relays or anything that the IAC runs through that can be checked?
 
lunchb0x said:
I noticed that when the IAC is unplugged the car does not cut out like it has been.
......Still only cutting out once and only after the car is started, does not happen again while running.
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IAC Unplugged - IAC (Idle Air Control) is for idling...once throttle is pressed downward, and if throttle switch is set correctly, IAC is not operational (no signal sent to IAC). Make sure your throttle switch is operational, as based upon OEM specs. Cutting out at 1900 RPM should have nothing to do with your IAC...your throttle plate is in control of air volume passing into intake.

Cutting Out - AMM and ECU's temp sensor determine amount of fuel going injectors.

I bought a 1990 240, parked it for several months, installed parts, and took injectors to injector shop for flow testing....it runs like it did when new.


So, try this: Techron? Complete Fuel System Cleaner
Techron? Named Best Fuel Additive in Autoweek's 2019 Readers' Choice Awards
https://www.chevronlubricants.com/en_us/home/products/techron-complete-fuel-system-cleaner.html
 
lunchb0x said:
I noticed that when the IAC is unplugged the car does not cut out like it has been.
Click to expand...

Footnote - IIRC, IAC's trigger signal is a Hz signal, which means an automotive grade multi-meter is required to examine a Hz signal.

If your electrical switch on throttle shaft is set correctly, once peddle is depressed, IAC becomes in-active.

Hence, one could check for and evaluate its Hz signal....but I doubt this is relevant. If IAC was working after peddle was depressed, logically, it would be doing it after engine was warmed up.
 
84B23F said:
So, try this: Techron? Complete Fuel System Cleaner
Techron? Named Best Fuel Additive in Autoweek's 2019 Readers' Choice Awards
https://www.chevronlubricants.com/en_us/home/products/techron-complete-fuel-system-cleaner.html
Click to expand...

I ran that a fill up or two ago. I am just about empty so I will pick up another one.

I picked up a AMM from PnP, cleaned it up and tossed it in the car. Still getting the cutout. Before swapping the AMM I noticed that when the car is cold the cut out moved up to about 3k RPM but once warmed up it cuts out at 1900 RPM.

I unplugged the battery while doing the MAF and the RPM gauge jumped to around 2k RPM when the key was turned on. With the car started the RPM gauge would not respond at all until warmed up.

I did the Tach test as you mentioned and nothing changed with the RPM gauge. It only responded once the engine was warm.

I've basically replaced everything aside from injectors and hall sensor with new/known good ones. From what I've read the hall sensor doesn't cause a cutout like this, the car dies or doesn't start. Is this the only known way a hall sensor fails?

Also, I hooked up a Noid light to the injector harness and all injectors had the same light and pulse intensity at idle and when revving up. I noticed that when the cut out happens the Noid light went out then came back.
 
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Based upon a diagram, the Chrysler box has one terminal for LH unit...I suspect this might be a tach signal, but it might be in a square wave format. Need a scope to scope this out....point here, is LH unit causing the effect, or is the Chrysler box causing this effect (Noid light went out).

Distributor - Find another one, and change out, if PnP don't charge too much...

Tach - Its negative comes off negative side of coil....If tach's coil wire can be removed from coil, I would remove it...there should be two wires there, one for Chrysler box, and one for tach. Otherwise, disconnect tach's wires, and tape them.
 
84B23F said:
Based upon a diagram, the Chrysler box has one terminal for LH unit...I suspect this might be a tach signal, but it might be in a square wave format. Need a scope to scope this out....point here, is LH unit causing the effect, or is the Chrysler box causing this effect (Noid light went out).

Distributor - Find another one, and change out, if PnP don't charge too much...

Tach - Its negative comes off negative side of coil....If tach's coil wire can be removed from coil, I would remove it...there should be two wires there, one for Chrysler box, and one for tach. Otherwise, disconnect tach's wires, and tape them.
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Yes, the LH2.2-paired Chrysler unit improved things over the LH2.0 used the previous year by sending the tach signal from ignition to fuel on a low level voltage (square wave), separate wire. The B23's fuel system got that info through a shielded wire directly from the coil negative.

One issue that has plagued Chrysler/LH2.2 (85-88) cars is that RPM signal being lost where the two harnesses join under the intake manifold -- gray wire I think -- there's a connector that gets grody. If I remember my junkyard trips, the connector has both the gray wire for RPM and orange wire for TPS, but I haven't owned any of these lh2.2 cars either. Somehow I don't think that connector is the OP's issue here.

But, in skimming this thread I want to ask the question about the "fuel cut" assertion. How does one know a cut is fuel and not spark? Aren't the results going to feel the same? Power stops?

So I looked for some indication OP had the timing light running when the cut occurred. That suspicion goes toward your recommendation to get that tach out of the circuit, or swap the dizzy. Ignition cut out maybe?
 
Thanks for the replies, I really do appreciate the help. I finally got some time work on the Volvo.

I swapped out the distributor with one from a '87 240 and installed a new Hall Sensor on it. The cut still happens, but I noticed the car seems to run a bit better. Before at idle when I'd press the throttle to the floor it would bog out and feel like it wanted to die, now it revs up with no hesitation.

I removed the tach wire from the coil and no change. I also inspected the harness connector under the manifold and it didn't look corroded or oily. I did clean it with some MAF cleaner. I haven't noticed the tach acting funny since, but it was also a random occurrence.

I had my roommate hold a spark plug to the strut tower and spark appears strong and does not cut out when the motor does. When I tested fuel pressure the pressure did not drop when the cut happened. I'm guessing the ECU is cutting the injectors?
 
lunchb0x said:
I'm guessing....
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Coil - On its negative terminal, Chrysler box grounds it momentary, and Tach uses this ground pulse to determine RPM. As RPM increases, the number of ground pulses increase. When Chrysler box shuts off its ground to coil, the coil's "stored" energy seeks out a path to ground, which is a spark plug.

RE: "....only do this the first time I take off after starting the car."

With a cold engine, start engine, and let it idle for say 5 minutes, then drive it. If the same issue, then on another day, start a cold engine, and let it idle for say 10 minutes, then drive it.
 
You might have to splice in a spare female to use this in-line, or tap in at the ECU plug to watch it driving, but having it might prove your ECU is cutting fuel at the injectors.

noid01.jpg


noid02.jpg


noid03.jpg
 
84B23F said:
With a cold engine, start engine, and let it idle for say 5 minutes, then drive it. If the same issue, then on another day, start a cold engine, and let it idle for say 10 minutes, then drive it.
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I'll do that this weekend and see what happens. Engine temperature hasn't been a factor when it comes to the cut out, it will do it cold or warm. The random issue with the tach acting up has only seemed to happen when the car is cold, after warming up for a bit it will begins to work normally.
 
lunchb0x said:
... tach acting up....
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I would suggest disconnecting that tach, and hookup another tach, and watch it.

Find someone with a Dual-Trace Oscilloscope so spark and fuel could be evaluated. Maybe Cleanflametrap could explain how to set it up.
 
I finally got around to working on the car again. I went through all the grounds for everything and cleaned them and insured they were tight. I remember previously when I disconnected the Idle Air Control motor that the car would not cut out, so I did that again. At the time I thought it was just a fluke since there were a few other issues if I remember correctly.

I disconnected the electrical connector for the IAC and the car seems to idle better and the car does not cut. I reconnected it while the car was running then rev'd up the car and it cut out like it usually does. However with it disconnected again the car does not cut out.

I inspected the harness a while back and fixed any bare wires or corroded shielding I found, but I don't think I looked for corrosion in the connectors themselves. I am going to take a look at that as well as try to find out what the voltage/ohms are supposed to be for the IAC through its usage so I can see if there's an issue there. I swapped the IAC itself with a spare and it still cuts.
 
Cwazywazy said:
I dunno if you've already tried it, but have you messed with the TPS? Does it cut with it disconnected?
Click to expand...

I've adjusted it so that I hear the click when the throttle plate is barely moved. I also swapped it and the throttle body with one from my roomates car. I swapped over the whole unit as is from his car as it functioned fine, still had the cut issue.

I don't think I've mentioned it before but since I've had this cut out issue the idle drops a little when the A/C is turned on. From my reading it is supposed to raise 50rpm or so when turned on. I've also noticed when the motor is cold the idle does not raise at all. If I remember correctly before having this cutout issue the idle would raise up when the motor was cold and lower down to normal as it warmed up.
 
So I tested the voltage on the harness plug and I get 5v on the brown and white-blue wires with the IAC unplugged and car running. With the IAC plugged in and car running the voltage drops to millivolts. I plugged the spare IAC into the harness and started the car running, the IAC motor never moves. I bench tested it and it moves when voltage is applied to it. I've got a wiring issue with the IAC it seems.
 
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