Help! Might I have a bad ECU?
11-01-13, 06:31 PM
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Help! Might I have a bad ECU?
One word describes the symptoms this car has shown: inconsistent.
So here's the deal: I pulled my current GSL SE out of some dudes yard and towed it home back in May. The story he gave me was something along the lines of "daily drove it for a while, one day it wouldn't start, cranked it till the battery died, towed it home and its sat ever since".
Me and a friend who is more familiar with rotaries had always thought it was just flooding because of dirty/leaky injectors. It would start, and run (we even drove it around a bit) but if you shut it off, it would't start until it was allowed to sit for seemingly enough time for flooded gas to evaporate. Plugs had fuel on them at the time, but we weren't sure how much there should be to deem the engine flooded.
So I decided to store the car down at a friends shop to keep it dry and benefit form a lift and air tools etc... Did a clutch job, revamped the cooling system and did some interior work, then finally got a chance to fire it up for the first time a couple weeks ago.
This is where things get interesting... We had the exhaust off for the clutch job, so it was running just a header. Cranked it over and it fired right up! Even idled nicely at just under 1k RPMs. I hopped in and gave it a few revs after it had sat idling for a bit. It came back to idle then started to sputter and proceeded to die. So we rolled it back into the shop and called it a night.
Went back on wednesday to tie up a few loose ends, and take it for a spin. Loose ends were tied, rolled it outside, cranked it and it fired right up again! This time, though, it jetted up to about 2800 RPMs, then started to sputter down and died. Did this a couple more times. I tried getting on the gas in order to hold it up. Felt smooth at around 4k RPMs, but if I let it go down it would start feeling really rough. Then when I let off it died.
Went to fire it up again, and this time no start. So we wised up a bit... Cranked it again and noticed there was no fuel pump noises indicating its activity. Pulled the plugs and found they had fuel on them but not very much. Cleaned them off then my buddy ground them to the body to see if we were getting spark. Nothing. Went to crank it again, and noticed there was no movement of the tach, which was previously working.
Another tidbit that I realized after putting some thought into things, is that when it does fire up, it always idles at a slightly different speed (usually between 1k-3k).
So, it almost seems as though the ECU isn't getting power. The electrical stuff under the hood seems botched at best. If that isn't the cause of the issue, it is very possible that it might be the cause of an ECU frying.
Where should I start looking? Grounds? Certain wires? Fuses? A few things for further consideration: was run with just the header and no heat shields on the underbody. Possible that the ECU area got really hot? There was also, at one point, a lot of water coming into the car. Corroded things I should look for? Also, dash warning lights appear to be functioning...
Mmmm...ended up long winded as usual, sorry. Any and all ideas are welcome. Car now resides at home in my garage so it is much more accessible FYI. Thanx!
So here's the deal: I pulled my current GSL SE out of some dudes yard and towed it home back in May. The story he gave me was something along the lines of "daily drove it for a while, one day it wouldn't start, cranked it till the battery died, towed it home and its sat ever since".
Me and a friend who is more familiar with rotaries had always thought it was just flooding because of dirty/leaky injectors. It would start, and run (we even drove it around a bit) but if you shut it off, it would't start until it was allowed to sit for seemingly enough time for flooded gas to evaporate. Plugs had fuel on them at the time, but we weren't sure how much there should be to deem the engine flooded.
So I decided to store the car down at a friends shop to keep it dry and benefit form a lift and air tools etc... Did a clutch job, revamped the cooling system and did some interior work, then finally got a chance to fire it up for the first time a couple weeks ago.
This is where things get interesting... We had the exhaust off for the clutch job, so it was running just a header. Cranked it over and it fired right up! Even idled nicely at just under 1k RPMs. I hopped in and gave it a few revs after it had sat idling for a bit. It came back to idle then started to sputter and proceeded to die. So we rolled it back into the shop and called it a night.
Went back on wednesday to tie up a few loose ends, and take it for a spin. Loose ends were tied, rolled it outside, cranked it and it fired right up again! This time, though, it jetted up to about 2800 RPMs, then started to sputter down and died. Did this a couple more times. I tried getting on the gas in order to hold it up. Felt smooth at around 4k RPMs, but if I let it go down it would start feeling really rough. Then when I let off it died.
Went to fire it up again, and this time no start. So we wised up a bit... Cranked it again and noticed there was no fuel pump noises indicating its activity. Pulled the plugs and found they had fuel on them but not very much. Cleaned them off then my buddy ground them to the body to see if we were getting spark. Nothing. Went to crank it again, and noticed there was no movement of the tach, which was previously working.
Another tidbit that I realized after putting some thought into things, is that when it does fire up, it always idles at a slightly different speed (usually between 1k-3k).
So, it almost seems as though the ECU isn't getting power. The electrical stuff under the hood seems botched at best. If that isn't the cause of the issue, it is very possible that it might be the cause of an ECU frying.
Where should I start looking? Grounds? Certain wires? Fuses? A few things for further consideration: was run with just the header and no heat shields on the underbody. Possible that the ECU area got really hot? There was also, at one point, a lot of water coming into the car. Corroded things I should look for? Also, dash warning lights appear to be functioning...
Mmmm...ended up long winded as usual, sorry. Any and all ideas are welcome. Car now resides at home in my garage so it is much more accessible FYI. Thanx!
Last edited by autobahn_don; 11-01-13 at 06:37 PM.
11-01-13, 07:24 PM
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well i think my first step would be to look at spark. the fuel pump is triggered from the ECU, which gets the RPM signal from the trailing ignitor. so no trailing ignitor = no fuel, no tach.
its a good first thing to look at
its a good first thing to look at
11-01-13, 07:32 PM
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We did in fact pull one trailing plug and got nothing. The other two lead plugs also were not creating spark. I had seen a snippet of information about the trailing ignitor providing that signal. Where/what does it get that signal from?
11-02-13, 10:13 AM
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the ECUs tach signal is on the trailing coil, i think the - side. ignitor fires the coil...
11-02-13, 11:22 AM
#5
Check the little cone shaped filter on the inlet of the fuel pump
One word describes the symptoms this car has shown: inconsistent.
So here's the deal: I pulled my current GSL SE out of some dudes yard and towed it home back in May. The story he gave me was something along the lines of "daily drove it for a while, one day it wouldn't start, cranked it till the battery died, towed it home and its sat ever since".
Me and a friend who is more familiar with rotaries had always thought it was just flooding because of dirty/leaky injectors. It would start, and run (we even drove it around a bit) but if you shut it off, it would't start until it was allowed to sit for seemingly enough time for flooded gas to evaporate. Plugs had fuel on them at the time, but we weren't sure how much there should be to deem the engine flooded.
So here's the deal: I pulled my current GSL SE out of some dudes yard and towed it home back in May. The story he gave me was something along the lines of "daily drove it for a while, one day it wouldn't start, cranked it till the battery died, towed it home and its sat ever since".
Me and a friend who is more familiar with rotaries had always thought it was just flooding because of dirty/leaky injectors. It would start, and run (we even drove it around a bit) but if you shut it off, it would't start until it was allowed to sit for seemingly enough time for flooded gas to evaporate. Plugs had fuel on them at the time, but we weren't sure how much there should be to deem the engine flooded.
When you pull the fuel hose, sometimes the filter will stick inside the hose but it's easy to get out.
If that is your problem, then you either need to clean your tank or do what I did which was buy a large filter for the inlet side of the fuel pump. The hoses are a large size so have an example size when you go to the parts guy if that's the problem.
11-03-13, 07:08 PM
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Check the little cone shaped filter on the inlet of the fuel pump, your car sounds like mine when it was clogged and since you car sat for a while, it's possible it's plugged.
When you pull the fuel hose, sometimes the filter will stick inside the hose but it's easy to get out.
If that is your problem, then you either need to clean your tank or do what I did which was buy a large filter for the inlet side of the fuel pump. The hoses are a large size so have an example size when you go to the parts guy if that's the problem.
When you pull the fuel hose, sometimes the filter will stick inside the hose but it's easy to get out.
If that is your problem, then you either need to clean your tank or do what I did which was buy a large filter for the inlet side of the fuel pump. The hoses are a large size so have an example size when you go to the parts guy if that's the problem.
[QOUTE=j9fd3s;11612509]the ECUs tach signal is on the trailing coil, i think the - side. ignitor fires the coil...[/QUOTE]
Ok, I'll check it out
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