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Manfreds78bay
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Joined: February 27, 2009
Posts: 754
Location: PNW
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 Posted: Thu Feb 09, 2017 5:44 pm Post subject: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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So I've been doing a lot of research on here and I think I've figure it out, but wanted some feed back.
78 FI 2.0l. Rebuilt about 8 years ago. I replaced the temp sensor 2 during the rebuild
She won't start. She turns over just fine. Brand new battery. Days old. I replaced it after 6 years.
I discovered she will start very easily when I unplug the AFM. And she will run without dying. After warm, running between 5 and tens minutes, she will die instantly if I plug the AFM back in.
I tested the AFM. Everything is within spec.
I tested the connections to the Double Relay when ignition is on but not running. Got good voltage.
I tested that the fuel pump will run while starting by turning on the ignition and opening the flap in the AFM. the pump continued to run.
I tried starting the bus with the Temp sensor 2 grounded when engine was cold and warm. She refused to run.
However if I warm the engine, then plug the AFM in with the Temp Sensor 2 unplug, she runs. She runs very rich, but she runs.
I tested the temp sensor 2. She seems just out of spec. Would being just out of spec cause it to not start?
The only thing I have done recently was to replace the brake booster check valve.
I assume my ignition is fine since she starts with out issue when unplugged from the AFM. I have not checked my fuel pressure, but since she will run while plugged into the AFM, I assume the pressure is more or less fine.
The only conclusion I can draw is a bad temp sensor 2 but I'm not completely sold. She should run fine when warm with the temp sensor plugged in. Maybe I should try letting the engine run for like 15 minutes, plug the TS2 in, and then try plugging in the AFM.
does anyone have any other theories?
I'm moving to Oregon in 24 days and I need to get this thing back on the road by then.
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1978 2.0L FI Campmobile
1982 AMC Eagle SX4 4.2L FI |
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Randy in Maine
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Joined: August 03, 2003
Posts: 34890
Location: The Beach
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| Posted: Thu Feb 09, 2017 5:52 pm Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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Put that dwell meter on the green points wire and tell us what it reads.
Have you done a fuel pressure test? |
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busdaddy
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Joined: February 12, 2004
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Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Thu Feb 09, 2017 5:53 pm Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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Your issue sounds like excess fuel pressure, but trying another TS2 wouldn't hurt.
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Willems
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Wildthings
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Joined: March 13, 2005
Posts: 50338
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| Posted: Fri Feb 10, 2017 8:58 am Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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Your guys' problem has cropped up before, but I don't recall the solution at this point. A search might turn up the answer for you. I don't remember any recent posts on this, but several years ago it seemed a similar problem was cropping up every few months. |
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Manfreds78bay
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Joined: February 27, 2009
Posts: 754
Location: PNW
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| Posted: Fri Feb 10, 2017 10:24 am Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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| busdaddy wrote: |
| Your issue sounds like excess fuel pressure, but trying another TS2 wouldn't hurt. |
Thanks Busdaddy. I did a fuel pressure test this morning. With the pump on not running I got 38 psi. Which is on the high side but still will in spec.
I found an old TS 2 and plugged it in and would not start. I unplugged the TS2 and she ran the same. She's running really rough with the AFM plugged in. The fuel pressure gauge was jumping around quite a bit but it looked to be around 35 PSI which is high.
My gas gauge doesn't work so to verify I had at least a half tanf full of gas, I filled up the tank. I ended up over filling it to the point that fuel went into the venting system. I found one of the hoses under the driver side was bad and leaking. So I may have found a vacuum leak, I'm not sure if this is causing the problem but I'm sure it doesn't help. I'm going to verify the fuel return line isn't blocked as well. Also going to check the fuel filter. But I did a check on this already. Blew air through it and it seemed to be fine. I have a new one I'll switch out just to see if that's the issue.
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1978 2.0L FI Campmobile
1982 AMC Eagle SX4 4.2L FI
Last edited by Manfreds78bay on Fri Feb 10, 2017 10:39 am; edited 2 times in total |
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Manfreds78bay
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Joined: February 27, 2009
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Location: PNW
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| Posted: Fri Feb 10, 2017 10:25 am Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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| Randy in Maine wrote: |
Put that dwell meter on the green points wire and tell us what it reads.
Have you done a fuel pressure test? |
Hi Randy. I have a petronix, so I don't think the issue with the dwell. I suppose the petronix could have gone bad.
I'll see if I can test it.
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1978 2.0L FI Campmobile
1982 AMC Eagle SX4 4.2L FI |
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Manfreds78bay
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| Posted: Fri Feb 10, 2017 10:28 am Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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| Wildthings wrote: |
Your guys' problem has cropped up before, but I don't recall the solution at this point. A search might turn up the answer for you. I don't remember any recent posts on this, but several years ago it seemed a similar problem was cropping up every few months. |
Thanks, Wildthings. I have been doing quite a bit of searching already before I considered posting. It's frustrating. I have found a lot of people have posted similar issues but never post the resolution. Oh well. I'll make sure to post my resolution.
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1978 2.0L FI Campmobile
1982 AMC Eagle SX4 4.2L FI |
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Manfreds78bay
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Joined: February 27, 2009
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| Posted: Fri Feb 10, 2017 10:28 am Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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Thanks for the info!
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1978 2.0L FI Campmobile
1982 AMC Eagle SX4 4.2L FI |
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Wildthings
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| Posted: Fri Feb 10, 2017 10:39 am Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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| Suck on the vacuum hose to the FPR making sure it isn't full of gas first. It should hold vacuum when you suck on it. |
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Randy in Maine
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Joined: August 03, 2003
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| Posted: Fri Feb 10, 2017 12:18 pm Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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If it were me, I would be closely looking at the plug in connections for the AFM and the ECU to see if there is a pushed in pin connector or something that is not making a good electrical connection. I would use your continuity meter and the ohm meter to find out if you have a bad wire int he engine wiring harness or perhaps one that is down to a single strand of wire.
While you are in there, see if you can test the TSII at the ECU plug in. Make sure that electrical connection (at the TSII plug in) is 100%.
I trust you have already cleaned and tightened the electrical connections at the battery, the starter and the chassis ground strap. All of those are critical. |
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Manfreds78bay
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Joined: February 27, 2009
Posts: 754
Location: PNW
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| Posted: Fri Feb 10, 2017 3:15 pm Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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| Randy in Maine wrote: |
If it were me, I would be closely looking at the plug in connections for the AFM and the ECU to see if there is a pushed in pin connector or something that is not making a good electrical connection. I would use your continuity meter and the ohm meter to find out if you have a bad wire int he engine wiring harness or perhaps one that is down to a single strand of wire.
While you are in there, see if you can test the TSII at the ECU plug in. Make sure that electrical connection (at the TSII plug in) is 100%.
I trust you have already cleaned and tightened the electrical connections at the battery, the starter and the chassis ground strap. All of those are critical. |
Thanks Randy. With your advice I just went through and started testing all the connections and continuity for the FI harness from the CPU plug. Everything was checking out fine. The FI wire hardness is almost new. I rebuilt it 2 years ago as a winter project. So I thought I might have left something a little loose in the CPU plug in.
Also put a vacuum pump on the FPR, thanks WT! It held plenty of vacuum. Zero leaks. Which is awesome because it looks like its a 1000 years old. Probably should pick up a new one. It might have been stuck and the vacuum test knocked something loose.
Scratched my head a bit. Then I saw I had not plugged in the engine breather tube back into the air filter box. I removed it when I tested AFM and forgot to put it back. I figured I would put it back on and try and start her with everything hooked up.
She fired up just as before all this nonsense happened. I double checked the TS2 sensor she was plugged in and so was the AFM. WTF!!!! The fuel PSI read 31 while warm which is on the high side but with in spec. She revs up just as before.
I still don't know what the issue is! Maybe i just blew the dust off something or plugged something back in that was loose.
I'm going to make sure all the connections are solid before I leave on my trip.
Thanks everyone for your help on this one. If I find anything that positively points to the issue, I'll update this thread.
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1978 2.0L FI Campmobile
1982 AMC Eagle SX4 4.2L FI |
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Randy in Maine
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| Posted: Sat Feb 11, 2017 6:59 am Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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| Glad it worked out for a cheap fix! |
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JaimeH 
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Location: Canterbury, NH
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| Posted: Sat Feb 11, 2017 9:37 am Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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This should be a go-to thread when folks ask about switching from FI to carb(s) Most of the issues with FI are simple, just hard to spot.
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airschooled
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| Posted: Sat Feb 11, 2017 4:21 pm Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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Hang on, which hose are we talking about? The crankcase breather hooks into the S-boot. The air cleaner has one or two hoses; the large plastic one from the charcoal canister won't affect running, and the small one (if you have it) from the throttle body/distributor advance wouldn't affect starting a cold engine unless your mixture is out of whack....
Robbie
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Manfreds78bay
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Joined: February 27, 2009
Posts: 754
Location: PNW
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| Posted: Mon Feb 20, 2017 6:42 am Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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| asiab3 wrote: |
Hang on, which hose are we talking about? The crankcase breather hooks into the S-boot. The air cleaner has one or two hoses; the large plastic one from the charcoal canister won't affect running, and the small one (if you have it) from the throttle body/distributor advance wouldn't affect starting a cold engine unless your mixture is out of whack....
Robbie |
The hose from the oil breather to the Sboot. It probably wasn't the issue, it just caused a no start after I checked other things.
However, I think I may have found the issue. I was putting everything back together over the weekend. And it wouldn't start again. I noticed the hose that goes from the air filter to the top charcoal canister did not have a tight fit at the air cleaner. I fixed it and she started right up. So that may have been the issue.
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1978 2.0L FI Campmobile
1982 AMC Eagle SX4 4.2L FI |
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Manfreds78bay
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| Posted: Mon Feb 20, 2017 6:46 am Post subject: Re: No Start Issue Leaning Towards Bad Temp Sensor 2 |
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| JimmieH wrote: |
| This should be a go-to thread when folks ask about switching from FI to carb(s) Most of the issues with FI are simple, just hard to spot. |
Yeah I am a big fan of FI. Carbs I think are great for certain apps. But to convert from FI to carbs is a waste of time and money.
It's a very simple system, but finding gremlins can be tough. I've had the bus for 7 years now and this is the first time I've had an issue.
I probably am due to buy new hoses fuel and vacuum.
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1978 2.0L FI Campmobile
1982 AMC Eagle SX4 4.2L FI |
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