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emitor81
Samba Member
Joined: June 02, 2009
Posts: 31
Location: CA
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 Posted: Thu Sep 16, 2010 5:58 pm Post subject: Dead ECU? |
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How does one know if the ECU is dead???
my '72 FI SQBK has spark, has fuel pressure, distributor trigger points are doing their job (read about it in the sticky), the ground 'spider' is grounded well, the relay to the ECU is doing it's job, the injectors work (put a small battery to them), but the injectors do not seem to be triggering.
i had the injectors out, cranked the engine and no fuel mists.
I tried looking in the sticky.
How do you check if the ECU is dead?
Thanks
Edit: Answers are on page 5 in bold.
Last edited by emitor81 on Fri Nov 12, 2010 3:08 pm; edited 1 time in total |
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Tram
Samba Socialist
Joined: May 02, 2003
Posts: 23022
Location: Northwest of Normal
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| Posted: Thu Sep 16, 2010 6:03 pm Post subject: Re: Dead ECU??? |
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| emitor81 wrote: |
How does one know if the ECU is dead???
my '72 FI SQBK has spark, has fuel pressure, distributor trigger points are doing their job (read about it in the sticky), the ground 'spider' is grounded well, the relay to the ECU is doing it's job, the injectors work (put a small battery to them), but the injectors do not seem to be triggering.
i had the injectors out, cranked the engine and no fuel mists.
I tried looking in the sticky.
How do you check if the ECU is dead?
Thanks |
You can check function and continuity through the wiring harness using a VOM on the numbered wires at the big plug.
If EVERYTHING checks out OK but the car doesn't run, it's likely the ECU. It's not a common failure item though. It could be a broken wire in the harness.
What suffix do you have on your ECU? Is it an "E"?
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| Bryan67 wrote: |
| Just my hands. And a little lube. No tools. |
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emitor81
Samba Member
Joined: June 02, 2009
Posts: 31
Location: CA
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| Posted: Thu Sep 16, 2010 6:14 pm Post subject: |
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CU15X is on the ECU. I don't see anything else on it.
"You can check function and continuity through the wiring harness using a VOM on the numbered wires at the big plug"
Where is that big plug with the numbered wires?
Am I just checking that there is resistance from one wire to another? |
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Tram
Samba Socialist
Joined: May 02, 2003
Posts: 23022
Location: Northwest of Normal
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| Posted: Thu Sep 16, 2010 6:21 pm Post subject: |
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| emitor81 wrote: |
CU15X is on the ECU. I don't see anything else on it.
"You can check function and continuity through the wiring harness using a VOM on the numbered wires at the big plug"
Where is that big plug with the numbered wires?
Am I just checking that there is resistance from one wire to another? |
Not resistance- continuity. Unplug the plug at the ECU and use your Bentley current flow diagram to see how things test. An "open loop" reading on a wire will tell you it's broken.
How many prongs at your throttle switch- 4 or 5?
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| Bryan67 wrote: |
| Just my hands. And a little lube. No tools. |
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emitor81
Samba Member
Joined: June 02, 2009
Posts: 31
Location: CA
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| Posted: Thu Sep 16, 2010 6:27 pm Post subject: |
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5 at the throttle switch.
Ok I see what you mean about the continuity. Alright, sounds good.
If the ECU is dead:
What's the price on an ECU?
Would i just be throwing money away if I bought a used one from the classifieds? |
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Tram
Samba Socialist
Joined: May 02, 2003
Posts: 23022
Location: Northwest of Normal
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| Posted: Thu Sep 16, 2010 6:34 pm Post subject: |
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| emitor81 wrote: |
5 at the throttle switch.
Ok I see what you mean about the continuity. Alright, sounds good.
If the ECU is dead:
What's the price on an ECU?
Would i just be throwing money away if I bought a used one from the classifieds? |
You have an "E" ECU. I have several good used control units and harnesses available. See what your test reveals.
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| Bryan67 wrote: |
| Just my hands. And a little lube. No tools. |
Those who can- do.
Those who can't? Subaru. |
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emitor81
Samba Member
Joined: June 02, 2009
Posts: 31
Location: CA
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| Posted: Thu Sep 16, 2010 6:44 pm Post subject: |
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thanks man, I'll have to get back to you tomorrow.
thank you |
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emitor81
Samba Member
Joined: June 02, 2009
Posts: 31
Location: CA
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| Posted: Wed Oct 13, 2010 4:49 pm Post subject: |
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I just want this thing to run. I'm frustrated. I would like to get it running as an FI car but I know I would have it running in no time if it had carbs. It's frustrating.
I think it is the ECU. I tested and it doesn't seem to have any breaks in the wires.
Are there specific wires that would completely keep the ECU from functioning if not connected properly?
Tram I might buy an ECU from you. how much? and how much for a harness? I really don't want to spend too much on this car. I almost just want to get rid of it. |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 23531
Location: Oklahoma City
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| Posted: Mon Oct 18, 2010 8:33 am Post subject: |
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| emitor81 wrote: |
I just want this thing to run. I'm frustrated. I would like to get it running as an FI car but I know I would have it running in no time if it had carbs. It's frustrating.
I think it is the ECU. I tested and it doesn't seem to have any breaks in the wires.
Are there specific wires that would completely keep the ECU from functioning if not connected properly?
Tram I might buy an ECU from you. how much? and how much for a harness? I really don't want to spend too much on this car. I almost just want to get rid of it. |
Yes...its rarely the ECU. Yes..there have been a couple of failures recently....probably age....but in 99.999% of the time, its not the ECU.
If any of the ground wires at the gorund wire bundles under the intake on teh case centerline are corroded or loose...it can not start.
If the fuel injectoon trigger points (the three oin plug on the distributor) are corroded or dirty....it will not start. If the plug is loose of has poor connection at the distributor (common)...it will not start.
If you do not have proper fuel pressure (28-30 psi) it will not start. If the CHT is disconnected, has poor connection or is short (common on all three) it will not start. Ray |
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JSMskater
Samba Grease Gorilla
Joined: February 01, 2006
Posts: 5362
Location: Murrieta California
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| Posted: Tue Oct 19, 2010 1:52 pm Post subject: |
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| emitor81 wrote: |
I just want this thing to run. I'm frustrated. I would like to get it running as an FI car but I know I would have it running in no time if it had carbs. It's frustrating.
I almost just want to get rid of it. |
And you'll never have any fun OR get it running with that attitude. ask me how I know.
Take a step back and do some READING first. it will go a long long way in helping you figure out whats going on here. As Ray and Tram pointed out, it's usually NOT the ecu. Your injectors aren't firing. Ok.
lets start at the grounds for the injectors. leave the porcupine near the oil breather alone, and remove a plug from an injector, but remove the big plug from the ECU. Stick one probe to ground and the other in one of the holes. see what the VOM says for resistance. It should be either zero or infinite ohms. Now check the other one. One should be zero, and the other should be infinite. If both are zero or both are infinite, well we've found the problem! Do this to all the plugs.
If this test checks out for all 4, re-do the test on the distributor plug with a few changes. First, instead of one probe on ground, stick it on 12, at the big plug. then put the other probe in the middle hole for the distributor trigger contact plug. it should read zero ohms resistance. if not, theres the problem. Repeat this test for wires 21 and 22 respectively at the big plug (they are labeled on the plastic plug itself) and stick your other probe in either end of the 3 hole plug, one or the other until you know which is which. if any read infinite ohms, then the wire is shot and you're gonna need to run a jumper or find a used harness, or you can order one from me, but you said you didn't want to spend too much cash so running a jumper is cheapest, vs getting a new harness is the most expensive option.
take a breath, and just work the problem. being impatient will only ruin your focus and getting frustrated is silly, you're not an expert and its not a new car so don't expect it to "just work". even carbs won't "just work". you'll likely be just as frustrated tuning a pair of dual icts as you will doing a little wiring on the FI. relax.
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TOOB Member #3
I make D-jet FI connectors |
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Jeffy_Baja
Samba Member
Joined: October 16, 2010
Posts: 12
Location: Vancouver, WA
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| Posted: Tue Oct 19, 2010 3:20 pm Post subject: |
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| Hey, I have a complete FI system in a box from a running car. Dist, fuel pump, manifolds, sensors, ecu, everything minus harness (plus anything i forgot to list). Its from a 72 type 3. Make offer. |
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Tram
Samba Socialist
Joined: May 02, 2003
Posts: 23022
Location: Northwest of Normal
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| Posted: Tue Oct 19, 2010 4:37 pm Post subject: |
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| JEFFY_Type III wrote: |
| Hey, I have a complete FI system in a box from a running car. Dist, fuel pump, manifolds, sensors, ecu, everything minus harness (plus anything i forgot to list). Its from a 72 type 3. Make offer. |
He has a California Emissions car with the 5 prong throttle switch and "E" ECU. If yours is the same it'll work but if it's a Fed Emissions car it's all different.
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| Bryan67 wrote: |
| Just my hands. And a little lube. No tools. |
Those who can- do.
Those who can't? Subaru. |
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rosevillain
Samba Member
Joined: December 28, 2005
Posts: 1341
Location: roseville, ca
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| Posted: Wed Oct 20, 2010 9:11 am Post subject: |
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| emitor81 wrote: |
I just want this thing to run. I'm frustrated. I would like to get it running as an FI car but I know I would have it running in no time if it had carbs. It's frustrating.
I think it is the ECU. I tested and it doesn't seem to have any breaks in the wires.
Are there specific wires that would completely keep the ECU from functioning if not connected properly?
Tram I might buy an ECU from you. how much? and how much for a harness? I really don't want to spend too much on this car. I almost just want to get rid of it. |
Updates?
After checking everything else, find an ECU, install it, and see if that's your problem. Once everything else has been factored out, an ECU has to be replaced for troubleshooting.
I waited far too long to take this step with mine, and got quite frustrated. Now it's my daily driver.
If that's not your problem, you have a spare. |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 23531
Location: Oklahoma City
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| Posted: Wed Oct 20, 2010 11:15 am Post subject: |
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| rosevillain wrote: |
| emitor81 wrote: |
I just want this thing to run. I'm frustrated. I would like to get it running as an FI car but I know I would have it running in no time if it had carbs. It's frustrating.
I think it is the ECU. I tested and it doesn't seem to have any breaks in the wires.
Are there specific wires that would completely keep the ECU from functioning if not connected properly?
Tram I might buy an ECU from you. how much? and how much for a harness? I really don't want to spend too much on this car. I almost just want to get rid of it. |
Updates?
After checking everything else, find an ECU, install it, and see if that's your problem. Once everything else has been factored out, an ECU has to be replaced for troubleshooting.
I waited far too long to take this step with mine, and got quite frustrated. Now it's my daily driver.
If that's not your problem, you have a spare. |
Well put....BUT....the important part about what you said....is that everything (at least the most important ...wires, grounds, sensors, fuel pressure, vacuum leaks etc.) must be factored out before swapping the ECU. Just unplugging and and replugging it can actually temporarily mend a poor connection...causing you to believe the ECU was the culprit...when it in fact it may not be. This is very, very, very common. Ray |
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Tram
Samba Socialist
Joined: May 02, 2003
Posts: 23022
Location: Northwest of Normal
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| Posted: Wed Oct 20, 2010 12:00 pm Post subject: |
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Emitor, check your PMs.
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| Bryan67 wrote: |
| Just my hands. And a little lube. No tools. |
Those who can- do.
Those who can't? Subaru. |
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emitor81
Samba Member
Joined: June 02, 2009
Posts: 31
Location: CA
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| Posted: Thu Oct 21, 2010 7:44 pm Post subject: |
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Woah thanks guys... I hadn't checked in and I also haven't gotten any emails about me having messages (i'll have to check my setting on my profile).
Alright Update:
I have been reading and there's a grip load of info and reading to do.
Tram mentioned the Temp sensors would keep an ECU from doing anything.
I Tested the sensors and they tested alright. I then tested the wires one of the pins was just hanging on; no continuity. I fixed that now It's a live.
I need to do a tune up; oil, point/condenser, valves... and timing.
It didn't stay on for long and seems way off, so I played with the timing a bit. The Distributor is turned all the way. This made it better but needs a bit more. I'll pull it out and replace it as per the book and also check the advance to make sure its functioning.
It's so crazy that just that wire kept it from going. I will still need a harness and a spare ECU. it's coming along. |
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Tram
Samba Socialist
Joined: May 02, 2003
Posts: 23022
Location: Northwest of Normal
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| Posted: Thu Oct 21, 2010 8:33 pm Post subject: |
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| emitor81 wrote: |
Woah thanks guys... I hadn't checked in and I also haven't gotten any emails about me having messages (i'll have to check my setting on my profile).
Alright Update:
I have been reading and there's a grip load of info and reading to do.
Tram mentioned the Temp sensors would keep an ECU from doing anything.
I Tested the sensors and they tested alright. I then tested the wires one of the pins was just hanging on; no continuity. I fixed that now It's a live.
I need to do a tune up; oil, point/condenser, valves... and timing.
It didn't stay on for long and seems way off, so I played with the timing a bit. The Distributor is turned all the way. This made it better but needs a bit more. I'll pull it out and replace it as per the book and also check the advance to make sure its functioning.
It's so crazy that just that wire kept it from going. I will still need a harness and a spare ECU. it's coming along. |
Excellent work! 
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Немає виправдання для війни! Я з Україною.
| Bryan67 wrote: |
| Just my hands. And a little lube. No tools. |
Those who can- do.
Those who can't? Subaru. |
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rosevillain
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Joined: December 28, 2005
Posts: 1341
Location: roseville, ca
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| Posted: Thu Oct 21, 2010 8:45 pm Post subject: |
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Nice! Now tune as per the Bentley.
There are like 12 wires that will keep it from running. Everything matters. |
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emitor81
Samba Member
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Posts: 31
Location: CA
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| Posted: Thu Oct 21, 2010 8:46 pm Post subject: |
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It was all you Tram. I didn't think the heat sensors would keep it from running. I guess had I checked all the wires, not just some, from the harness I would have found it.
I just still cant believe it was just that one little wire. I still had the injectors out so I wired everything back up and checked for fuel out the injector. Man I was excited. |
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Tram
Samba Socialist
Joined: May 02, 2003
Posts: 23022
Location: Northwest of Normal
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| Posted: Fri Oct 22, 2010 12:58 am Post subject: |
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| emitor81 wrote: |
It was all you Tram. I didn't think the heat sensors would keep it from running. I guess had I checked all the wires, not just some, from the harness I would have found it.
I just still cant believe it was just that one little wire. I still had the injectors out so I wired everything back up and checked for fuel out the injector. Man I was excited. |
Wires are not there for no reason, Grasshopper!  See? Now you no longer need fear the D-jet system... just don't try to outthink it; life's too short.
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Немає виправдання для війни! Я з Україною.
| Bryan67 wrote: |
| Just my hands. And a little lube. No tools. |
Those who can- do.
Those who can't? Subaru. |
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