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funcar
Joined: 14 May 2014
Posts: 9
Location: Jay, NY
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 Posted: Wed Apr 27, 2016 12:08 pm Post subject: 1980 931 very reluctant to start 1-6 hrs after being driven |
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Fasteddie313
Joined: 29 Sep 2013
Posts: 2595
Location: MI
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| Posted: Wed Apr 27, 2016 1:23 pm Post subject: |
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| funcar wrote: | I have 1980 931 with original Bosch mechanical fuel injection. This is my first car with the Bosch system, and was probably driving underage the
last time I was behind the wheel of a car that didn't have electronics fuel injection. Not sure if the problem is the way I'm starting it, or if I should be trying to track down a real problem with the car, There are many posts in this forum about hot start and cold start problems, and my symptoms don't seem to perfectly match any of the fixes described (though it could be that I'm missing something). Sadly, I find myself writing to this forum (its been a great help for other mods and fixes) to ask the seemingly ridiculous question, "am I correctly starting my car" !
Here are the symptoms:
- Cold start: The car starts perfectly the first time I fire it up in a day. I pump the gas to the floor 3 times, turn the key, and its 100% reliable. This is true whether it sits for months or over night. So its "(very) cold start" is ok.
- Hot start: The car starts very well when hot - such as after I fill it with gas at a gas station, and its been sitting for 2-15 minutes. I turn the key, touch the gas, and it roars to life.
- "warm" start: in between "hot" and "cold", the car treats me to infinite uncertainty. After sitting 1-4 hours (or even 6 hours), it is very, very reluctant to start. I have been experimenting with different recipes - starting it as if it were cold, or as if it were hot. Typically I do a half-way in between, applying the gas half-way and turning the key. Sometimes it starts, but most often, it turns over endlessly and if I'm very, very lucky, it will slowly growl to a relucant start after trying many times, and for prolonged periods. The only real correlation I've found is that, if I'm parked in a spot that becomes a tow-away zone after a few hours, the car knows it, and will refuse to start. I'll drain the battery trying, and then have to beg a passer-by for a boost. It always starts eventually, but only if I am able to apply endless cranking with a boost.
For the longest time, I thought it was probably just that I didn't know the correct recipe for starting a Bosch injected car and I was either flooding it or not giving it enough gas. I could imagine that the engine is dead-cold after sitting for 6 hours, but there is still fuel somewhere that has not evaporated and is causing problems when I add more.
First Question: what is the best recipe to start this car when it is "warm" ??
Second Question: is it more likely that I have a problem with the car? If so, what is the best recipe to diagnose it and what is the most likely culprit?
Reading the posts here, I convinced myself that I might have a problem with the thermo-time switch not activating the start valve, so I implemented the fix described here: http://www.924.org/techsection/hot_s...roblem_fix.htm Pulling the valve to ground with a pushbutton switch doesn't create any change, so I am assuming that my thermo-time switch is already correctly doing that job.
The other likely candidate seems to be the warm up regulator.
If I had a "hot start" or "cold start" problem, I think I'd know which of these things to attack - but my car is perfect in both of these categories. With this "warm start" problem, I'm not sure where to start.
Thanks in advance to anyone who (1) has read this far and (2) has experience with this sort of issue and is willing to suggest a diagnosis. Hopefully you'll be rewarded by not having to give me a boost!
Blower - High-beam correlation:
Finally, one last completely unrelated query: my main console blower is weak -
can't keep my windshield from fogging up on a humid day... except when the headlights are switched to hi-beams! Has anyone seen this before? (the power of the blower is only good when hi-beams are on). The relays look like they have been mangled a little by the previous owner, so my first step will be to get in there with the voltmeter and see if I can find a correlation. Before starting that, thought I'd ask if anyone has seen this before (I find nothing searching the board for "high-beam AND blower"). |
It is your apostrophes and quotation marks that are not agreeing with this forum for some reason. Also your periods that you used here "on a humid day..." ...
Your apostrophes and quotation marks seem to be at a slightly different angle than mine..
Are you using some kind of other language keyboard or something like that?
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80 Turbo - Slightly Modified |
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funcar
Joined: 14 May 2014
Posts: 9
Location: Jay, NY
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| Posted: Wed Apr 27, 2016 1:30 pm Post subject: |
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thanks, fasteddie, for making the text of my post appear. I composed the text in mac's "textedit" console, so perhaps it created funny versions of standard ascii.
Regardless of my posting woes - can anyone shed light on my "warm start" issues?
thanks in advance! |
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Fasteddie313
Joined: 29 Sep 2013
Posts: 2595
Location: MI
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| Posted: Wed Apr 27, 2016 1:58 pm Post subject: |
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- Cold start: The car starts perfectly the first time I fire it up in a day. I pump the gas to the floor 3 times, turn the key, and its 100% reliable. This is true whether it sits for months or over night. So its "(very) cold start" is ok.
Pumping the pedal when the engine is not running does absolutely nothing. Carburetors have a pump accelerator enrichment that sprays fuel when you pump the throttle. CIS does not..
- "warm" start: in between "hot" and "cold", the car treats me to infinite uncertainty. After sitting 1-4 hours (or even 6 hours), it is very, very reluctant to start. I have been experimenting with different recipes - starting it as if it were cold, or as if it were hot. Typically I do a half-way in between, applying the gas half-way and turning the key. Sometimes it starts, but most often, it turns over endlessly and if I'm very, very lucky, it will slowly growl to a relucant start after trying many times, and for prolonged periods. The only real correlation I've found is that, if I'm parked in a spot that becomes a tow-away zone after a few hours, the car knows it, and will refuse to start. I'll drain the battery trying, and then have to beg a passer-by for a boost. It always starts eventually, but only if I am able to apply endless cranking with a boost.
Can you smell your exhaust after cranking for a bit with no start? Smell like fuel or no fuel?
Maybe you have an intake air leak that is not allowing the small amount of air sucked in during cranking to move the air metering plate enough to pass enough fuel to your injectors.
Check for intake leaks especially where the intake pipe attaches to the top of your turbo to the bottom left of your cylinder head. the small section should have a bracket to the engine like behind your timing belt that often goes MIA and allows an intake leak there..
Maybe you just have your AFR set too lean for it to provide enough fuel for it to start..
Set your AFR:
Open your hood and find the electrical test plug that is right up just infront of the firewall on the drivers side in the engine bay right in the corner next to the fender. It has 3 wires and terminates with a round plug. Put a dwell meter on the black wire pin of that plug, be careful not to short the other pins to eachother.
With the car idling at about 900 RPM(set that first, airscrew on the TB not the throttle stop) at operating temp you want your dwell meter to read about 45% for a good mixture. You must have a functioning O2 sensor and lambda system for this to work.
Adjust the AFR with the allen screw in between the rubber boot from the air metering plate to the air cleaner housing and the fuel distributor down that hole. IIRC it is a 3mm allen you need.
Adjust then cover the hole and check the meter. The hole must be plugged to read correctly and plugged to operate as it is a vacuum leak if it is not.
Another thing you can do to help you get started is to jump the fuel pump either by putting a jumper wire between pins 30 and 87 of your fuel pump relay or just sticking a standard 4 pin relay in the fuel pump relay spot with the key on.
Then go under your hood and take that air cleaner boot off of your air meter between it and the air filter housing to expose the air metering plate. With the fuel pump running jumped push that air metering plate down just a smidge to spray your injectors a tiny bit priming your engine with a touch of fuel to get it started..
That is assuming you have an under-fueling problem..
If you have an over fueling problem, flooding, then adjust your AFR (air fuel ratio) with the dwell meter method.
Also if you are flooding it is a good idea to pull your injectors, jump the fuel pump, and make sure your injectors are not leaking with the air metering plate at rest. You can put them in pop bottles and spray them by pushing that plate to make sure they all spray the same with nice cone patterns, measure their outputs compared to eachother, and make sure they are not leaking with the metering plate at rest.
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80 Turbo - Slightly Modified |
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Cedric
Joined: 27 Aug 2004
Posts: 2809
Location: Sweden
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| Posted: Wed Apr 27, 2016 3:22 pm Post subject: |
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It would probably be a good idea to check your fuel accumulator. Best way is to have a pressure tester, i dont have the numbers in front of me but it should sustain fuel pressure for a certain ammount of time, I think its 30 minutes. Also measure the termo switch, so it activating like it should. Try search this forum on those topics, there should be lots of help available 
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1980 924 Turbo
www.instagram.com/garagecedric/ |
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funcar
Joined: 14 May 2014
Posts: 9
Location: Jay, NY
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| Posted: Wed May 11, 2016 12:27 pm Post subject: |
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Thanks again for the suggestions and info. Please see below.
Sorry it took a while to get back on this - it takes me a while between iterations, because I keep the car out of town, and so don't drive this car often. I can only reproduce the problematic behaviour if I drive it twice separated by 0.5-5 hours.
| Quote: |
- "warm" start: in between "hot" and "cold", the car treats me to infinite uncertainty. After sitting 1-4 hours (or even 6 hours), it is very, very reluctant to start. I have been experimenting with different recipes - starting it as if it were cold, or as if it were hot. Typically I do a half-way in between, applying the gas half-way and turning the key. Sometimes it starts, but most often, it turns over endlessly and if I'm very, very lucky, it will slowly growl to a relucant start after trying many times, and for prolonged periods. The only real correlation I've found is that, if I'm parked in a spot that becomes a tow-away zone after a few hours, the car knows it, and will refuse to start. I'll drain the battery trying, and then have to beg a passer-by for a boost. It always starts eventually, but only if I am able to apply endless cranking with a boost.
Can you smell your exhaust after cranking for a bit with no start? Smell like fuel or no fuel?
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I cannot smell any fuel.
| Quote: |
Maybe you have an intake air leak that is not allowing the small amount of air sucked in during cranking to move the air metering plate enough to pass enough fuel to your injectors.
Check for intake leaks especially where the intake pipe attaches to the top of your turbo to the bottom left of your cylinder head. the small section should have a bracket to the engine like behind your timing belt that often goes MIA and allows an intake leak there..
Maybe you just have your AFR set too lean for it to provide enough fuel for it to start..
Set your AFR:
Open your hood and find the electrical test plug that is right up just infront of the firewall on the drivers side in the engine bay right in the corner next to the fender. It has 3 wires and terminates with a round plug. Put a dwell meter on the black wire pin of that plug, be careful not to short the other pins to eachother.
With the car idling at about 900 RPM(set that first, airscrew on the TB not the throttle stop) at operating temp you want your dwell meter to read about 45% for a good mixture. You must have a functioning O2 sensor and lambda system for this to work.
Adjust the AFR with the allen screw in between the rubber boot from the air metering plate to the air cleaner housing and the fuel distributor down that hole. IIRC it is a 3mm allen you need.
Adjust then cover the hole and check the meter. The hole must be plugged to read correctly and plugged to operate as it is a vacuum leak if it is not.
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To access this area, I pulled the air filter, and was surprized to find it full of junk (mouse droppings and mouse nest! The little critters had pulled in a bunch of pink fiberglass insulation from somewhere, and stuffed it in here. Note that this must have happened over last winter, because there was fiberglass elsewhere under the hood after parking it in a friend's garage (with mice and open insulation) for the winter - big mistake!) on the intake side of the filter. I worried this may have made it air-deprived and hoped it would fix the problem. Cleaning it out thoroughly did not change anything.
As a next step, I decided to richen the mixture slightly. I don't have a dwell meter (will borrow one as a next step), but I went ahead and adjusted the allen screw clockwise (for more fuel in the mixture) by 1/4 turn.
I haven't had a chance to test this yet (car was cold, so starts perfectly, when I did this).
| Quote: |
Another thing you can do to help you get started is to jump the fuel pump either by putting a jumper wire between pins 30 and 87 of your fuel pump relay or just sticking a standard 4 pin relay in the fuel pump relay spot with the key on.
Then go under your hood and take that air cleaner boot off of your air meter between it and the air filter housing to expose the air metering plate. With the fuel pump running jumped push that air metering plate down just a smidge to spray your injectors a tiny bit priming your engine with a touch of fuel to get it started..
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I pulled the air cleaner boot off, to see what this looks like, and whoa - it looks terrible in there.
The air sensor plate (in your description you called thi sthe air metering plate - I'm assuming it's the same thing) is covered in grime/oil,
http://i.imgur.com/pdezRht.jpg
though the plate feels good (bounces down easily with a tap of the finger), and seems to be functioning. Note that below the plate, there's also a lot of grime/oil
http://i.imgur.com/0A2qV46.jpg
The grime/oil is exclusively ABOVE the air filter (not on the intake side) and seems to be coming from the hose that connects the cannister behind
http://i.imgur.com/u5b7m33.jpg
It's hard to invent scenarios that cause the problem I'm having, while not affecting a hot start or a cold start. I wonder if this grime could somehow explain it. Perhaps when its dead cold, it is crusty and doesn't stick. When it's hot, it looses all its viscosity, and doesn't affect the sensor plate. However, when the system is slightly warm (hours after running - heat could stay in there a long time) it is viscous and "sticks" ?
Next time it doesn't start well, I'll pull this boot and see if the sensor plate resistance feels any different.
Any idea what the origin of this grime/oil is, what sort of problem it indicates, and whether it is likely to be related to the "warm" starting problems? It could just be that, since the filter intake was blocked with the mouse-nests, it created weird suction that pulled the oil up.
BTW, I'm using 15w40 regular (non-synthetic) oil, though I don't think this is relevant.
| Quote: |
That is assuming you have an under-fueling problem..
If you have an over fueling problem, flooding, then adjust your AFR (air fuel ratio) with the dwell meter method.
Also if you are flooding it is a good idea to pull your injectors, jump the fuel pump, and make sure your injectors are not leaking with the air metering plate at rest. You can put them in pop bottles and spray them by pushing that plate to make sure they all spray the same with nice cone patterns, measure their outputs compared to eachother, and make sure they are not leaking with the metering plate at rest.
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I also put a 12V LED on the thermo time switch (described in this fix http://www.924.org/techsection/hot_start_problem_fix.htm ) so that I could see if it is working properly - it does. When the car is hot, the LED is on (sensor produces 12V), and when it is COLD it is of (0V). When I'm "warm starting" the car and have troubles, it's typically in the 0V cold position, so articifially pulling this to 0V with the hot start problem fix does not change anything or help.
I made an mp3 recording of the car starting when it is "warm", and has trouble starting.
listen to: http://vocaroo.com/i/s1691GPfNpTN
In this example, it started easier than normal (it's usually more reluctant than this, and takes a lot more cranking).
Note that for a hot or cold start, the car idles very well, and I never need to tickle the car to keep it going. However, with the "warm start", as in this recording, it will die immediately if I take my foot off the gas. The idle is rough and ugly (listen near the end). Eventually, after driving a little, it'll improve and go back to normal.
OK - thanks, especially if you've read this far. Advice is much appreciated!, |
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funcar
Joined: 14 May 2014
Posts: 9
Location: Jay, NY
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| Posted: Wed May 11, 2016 12:48 pm Post subject: |
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| Cédric wrote: | | It would probably be a good idea to check your fuel accumulator. Best way is to have a pressure tester, i dont have the numbers in front of me but it should sustain fuel pressure for a certain ammount of time, I think its 30 minutes. Also measure the termo switch, so it activating like it should. Try search this forum on those topics, there should be lots of help available |
Thanks Cedric. I found this thread http://www.924board.org/viewtopic.php?t=41749 and will see if it is leaking. Following the threads, this seems to be associated primarily with hot start problems, not really with trouble starting many hours after running the car. Nevertheless, I appreciate the suggestion, will test it, and see if there's an issue there.
thanks! |
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