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1984 B23F injectors not firing

242Bleek

k-jet groupie
Joined
Jul 18, 2005
Location
Brooksville/Tampa, FL
Hello, trying to get my 84 240 with LH 2.0 up and running. Car was running previously but running poorly then finally died. Ive gone through everything on this car. Changed both fuel pumps, filter, checked all electrical connections at fuse panel etc. This car has a new oem wiring harness from volvo. I checked for spark and thats all good and well. I replaced injectors too. I go to check voltage at the fuel injectors and when I ground the test light to the body I see 12v when cranking from the power side of the injector plug. However when I ground the test light to the other side of the injector plug (ECM side) and crank it, I get a very dim, almost non existent light on test light. This indicates to me that the ECM is not grounding the injectors or doing a poor job of it.

I have checked every single pin on the ECM plug to verify continuity with a multimeter at every terminal including #13 which pulses the injectors, theres no signs of any crossing of wires in the harness, all grounds including the ones on the intake have been cleaned and greased. I have verfied that both the system relay and FP relay are working properly and all pins at both relays are giving/receiving all the correct inputs. I am now on my second ECM too with no changes, its a 510 ECM.

There is absolutely no reason the injectors shouldnt be getting ground as the ECM has been confirmed to be grounded properly. Theres literally nothing else to check, I have been working on these cars my entire life and have never seen this happen, I know 240's like the back of my hand. Im writing this as a last ditch effort and am hoping to get some different input on anything else I could check. Thanks
 
The ECM only grounds the injectors very briefly at low load / low speed, so an incandescent test light across the injector pins may only glow. A LED noid light will do better and blink on the short pulses.

Can you get it to start and stay running for a bit with starting fluid?

If you have 2 fire extinguishers and a helper, you can disconnect the coil +12v wire, undo the fuel rail (injectors still attached), put a baggie and bread tie over each injector, and crank it for a bit to see if all 4 are working and roughly the same. If you do this, please be _very_ careful.
no clogged injectors.jpg
 
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Ahh okay. I didn't realize that the incandescent test light wouldn't be a good indicator of injector function. I will try that test when I get back and post the results.

This car has the old style fuel rail with nowhere to really test for fuel pressure. I removed the feed line and it pumped a ton of fuel into a bucket. Do you think a bad FPR could cause this? I mean it would have to be so blown out that it just sends all the fuel right back to the tank. Crazier things have happened though.
 
Have you looked at the spark plugs? Are they wet with fuel or dry like they aren't getting any fuel? When testing for spark did you check at the spark plug end of the plug wire? I use a spare spark plug and plug it into the end of the wire and ground the body of the plug to the car.

Timing belt alignment all good?
 
Have you looked at the spark plugs? Are they wet with fuel or dry like they aren't getting any fuel? When testing for spark did you check at the spark plug end of the plug wire? I use a spare spark plug and plug it into the end of the wire and ground the body of the plug to the car.

Timing belt alignment all good?
Yes spark plugs are all dry or seemed dry. Definitely not wet. I put the plug in the end of the wire and grounded it and a bright spark was visible. Timing should be good as it has good compression and ran well before. I can double check though.
 
Ok then. If you have dry plugs then it's not getting fuel. I would start with the fuel pump relay and see that it gets powered up. Use a test light to make sure the circuit can carry the current. I would also look under the car for decayed wiring at the fuel pump.
 
Ok then. If you have dry plugs then it's not getting fuel. I would start with the fuel pump relay and see that it gets powered up. Use a test light to make sure the circuit can carry the current. I would also look under the car for decayed wiring at the fuel pump.
Thats the thing. It has two new pumps, both are powered up and pumping lots of fuel. Like I said I can't really check fuel pressure on this car. Relays are clicking and functioning as they're supposed to. There is 12v at both pumps and the injectors. I replaced decayed wiring at the main pump already.
 
Here's the diagram I use. It seems way too simple not to work.
 

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Hello, trying to get my 84 240 with LH 2.0 up and running. Car was running previously but running poorly then finally died. Ive gone through everything on this car. Changed both fuel pumps, filter, checked all electrical connections at fuse panel etc. This car has a new oem wiring harness from volvo. I checked for spark and thats all good and well. I replaced injectors too. I go to check voltage at the fuel injectors and when I ground the test light to the body I see 12v when cranking from the power side of the injector plug. However when I ground the test light to the other side of the injector plug (ECM side) and crank it, I get a very dim, almost non existent light on test light. This indicates to me that the ECM is not grounding the injectors or doing a poor job of it.

I have checked every single pin on the ECM plug to verify continuity with a multimeter at every terminal including #13 which pulses the injectors, theres no signs of any crossing of wires in the harness, all grounds including the ones on the intake have been cleaned and greased. I have verfied that both the system relay and FP relay are working properly and all pins at both relays are giving/receiving all the correct inputs. I am now on my second ECM too with no changes, its a 510 ECM.

There is absolutely no reason the injectors shouldnt be getting ground as the ECM has been confirmed to be grounded properly. Theres literally nothing else to check, I have been working on these cars my entire life and have never seen this happen, I know 240's like the back of my hand. Im writing this as a last ditch effort and am hoping to get some different input on anything else I could check. Thanks
Guessing you replaced wiring harness due to insulation falling off/bare wires? Did you replace the harness before or after it died? In other words has it been running with the new harness before it died?
 
Yes it ran well with new harness then died. Car has been sitting for a couple years and I've been trying to get it running again. When I say new I mean the harness is about 5 years old. It was replaced due to the original degrading as you can imagine.

Car has a new fuel tank, sending unit and in tank pump as well.
 
New gas, or couple years old? If old, does it smell OK?

And out of curiosity, I shot some pictures of what an incandescent test light looks like when connected across an injector. This is why a LED noid light is preferred.
[Disclaimer: this is on my bench, indoors, with a '937 LH2.4 Turbo ECU, and a 12v power supply, so not the same as your LH2.0]
Injectors with Incandescent Test Light.jpg
 
Given that it was running poorly before it died, and wouldn't restart, I might be thinking about possible MAF failure. Gotta spare, or access to one you could borrow? Assuming you also checked for fuel leakage from FPR in the vac hose.
 
All old gas is out of the car, took it out with the old tank. Thanks for posting that, the test light looks exactly like the one in your picture while cranking. The issue could be elsewhere. I'm thinking it's not building fuel pressure or gas could be free flowing back to the tank if the FPR is bad. I'm about to swap this fuel rail out for a newer style, its very annoying not being able to check fuel pressure. I will check a few more things and get back to this thread.
 
Given that it was running poorly before it died, and wouldn't restart, I might be thinking about possible MAF failure. Gotta spare, or access to one you could borrow? Assuming you also checked for fuel leakage from FPR in the vac hose.
I tried another maf as well. The car should at least start up even with the maf unhooked, which it didnt.
 
All old gas is out of the car, took it out with the old tank. Thanks for posting that, the test light looks exactly like the one in your picture while cranking. The issue could be elsewhere. I'm thinking it's not building fuel pressure or gas could be free flowing back to the tank if the FPR is bad. I'm about to swap this fuel rail out for a newer style, its very annoying not being able to check fuel pressure. I will check a few more things and get back to this thread.
Yes, annoying. My 84 had trouble 22 years ago forcing me to think it was critical to know fuel pressure, so at the suggestion of another forum member I fashioned an adapter from a junkyard fuel rail after searching in vain for the pieces Volvo suggests. But since then I've had some experience guessing at rail pressure by running the pumps only (no spark or cranking) and gently squeezing the rubber portion of the return line at the rail. Now if you do this while trying to crank it over, it may become very rich (your nose should tell you) if the injectors aren't clogged with varnish and they are firing, which is what I believe your test lamp did assure you of (see bobxyz's illustration of an incandescent test lamp displaying the small duty cycle pulse).

This is done with a later fuel rail, but I bet you can imitate with yours:

fuel0472.jpg


Stuck regulator below.

fuel4530.jpg



fpgauge28.jpg


The adapters to connect a gauge are easier to get nowadays, but the one I made works 25 years later.

adapt.jpg


I had a problem with the enrichment during cranking and found out later there was a service bulletin addressing this, but as difficult as it was to start, I imagine it might be impossible with a shorted ECT sensor (zero volts on ECU pin 2).

84startingEnrichment.jpg


Checking the orange wire with key on in LH2.0 proves the system relay is powering the AMM and enabling the ECU.


hattrick646.jpg
 
Well I was able to get her running tonight. Did the injector volume test in little bags and seen that only 3 and 4 were spraying. I went ahead and adjusted the pins on the injector plug and added dielectric grease and now they all fire, fixed that. Still wouldn't start so I cleaned up the plugs as they were all fouled bad. Then she started! But the car was running stupid rich and wouldn't even advance rpm past 2k or so. I unplugged the O2 sensor and it cleared up and ran decent again, not perfect but pretty good considering it had no O2 sensor hooked up. I just put a new sensor on, appearantly it already went bad after a whole 30 minutes of run time. Will be replacing it with a bosch next time. Thanks for all the help, much appreciated.
 
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