Also, I checked the number of clicks heard when slowly squeezing the vacuum cruise control bag and noting how many clicks the injectors make when the ignition is on, but no RPMs, which is a way to check the adjustment of the Throttle Position Sensor.
1976 Seville ECU problem, Hard Cold Start
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I am thinking that it is possible the fuel pressure was normal after warming up, but maybe when it hasn't run for a while the pressure is low.
I haven't had it checked under those conditions.
I read the in tank pump has a filter. And, since the in tank pump hasn't been pulled out, I assume the old filter may be clogged.
I think that is the next thing to go after.
When the car was at the dealer last summer they drained and filled the tank which they said smelled like turpentine.
The technician wrote on the receipt, I have to drive it more.
The fuel pressure regulator is not adjustable, but was replaced with a new one last summer.
I am thinking if the pressure is 1/2 or like 20 psi or lower while cranking the starter, maybe that points to a fuel pump problem. In this case the next pump to replace is the in tank pump.
However, I haven't gotten feedback from any technician who has worked on it that this was actually occurring this way.
I suggest then your next task is to do what is needed for the in-tank pump and filter and then test your fuel rail pressure
during cold start
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I recently spoke to Bruce Roe who has repaired/tested more of the original ECU's then most of us have seen cars which need them. He mentioned he had one recently which was an aftermarket replacement or was reworked without the original components. I know you are saying that they should work with more combinations than did the originals but if you still have the original I would send it to Bruce. He can repair/replace most of the original components and he can put the ECU through a lot of different evaluations tests. He's also very reasonable.
Back to the fuel pressure and pumps. I know the in tank pump was discussed but don't forget that there is a small piece of special submersible soft hose in the tank as well. If that starts to crack even if the pump is working there will be some pressure loss. The 38-40psig sounded to me like the proper pressure. I thought it was 40psig for these.
A couple of other details as I know: There are 8 injectors but I believe sets of 4 take turns firing. Second: Bruce told me once when we were discussing cold start that the pumps run for a few seconds with the key on. They then stop running while you are cranking. So my start procedure is turn the key to the on position for a few seconds without cranking and listen for a sound change. Once I hear the sound change I crank. After I changed both sensors the car starts in about 3 seconds.
There is still a chance, even with good sensors, the proper value isn't making it to the ECU. That's if there was an issue somewhere in the harness. Since you've changed the ECU a number of times I think I would try measuring the sensor resistance but at the plugs which normally plug into the ECU ( as opposed to just checking near the sensor). The table in the Service Manual is also light on precise values and there is obviously some range and you mentioned they measured within range. If you tell me the intake temp and what the sensor reads I can tell you how close that is to what I would say is typical of what I normally see.
Scott
Back to the fuel pressure and pumps. I know the in tank pump was discussed but don't forget that there is a small piece of special submersible soft hose in the tank as well. If that starts to crack even if the pump is working there will be some pressure loss. The 38-40psig sounded to me like the proper pressure. I thought it was 40psig for these.
A couple of other details as I know: There are 8 injectors but I believe sets of 4 take turns firing. Second: Bruce told me once when we were discussing cold start that the pumps run for a few seconds with the key on. They then stop running while you are cranking. So my start procedure is turn the key to the on position for a few seconds without cranking and listen for a sound change. Once I hear the sound change I crank. After I changed both sensors the car starts in about 3 seconds.
There is still a chance, even with good sensors, the proper value isn't making it to the ECU. That's if there was an issue somewhere in the harness. Since you've changed the ECU a number of times I think I would try measuring the sensor resistance but at the plugs which normally plug into the ECU ( as opposed to just checking near the sensor). The table in the Service Manual is also light on precise values and there is obviously some range and you mentioned they measured within range. If you tell me the intake temp and what the sensor reads I can tell you how close that is to what I would say is typical of what I normally see.
Scott
Scott, thanks for your deep thoughts on this matter. I think you and ZR-1 have a good understanding of the problem I have on this vehicle and good possible solutions.
I will follow up with what I find, when it gets a little warmer outside in the Spring of 2021 if I learn anymore about the subject.
Duane Wong
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Hi Duane,
I totally understand the "gets a little warmer outside" comment
I'm waiting for that event myself for some car work.
I don't know if we can send attachments in a PM or I think they call them DM's here but I have Bruce's entire list of ECU PNs. I spoke to him and he told me I can send it to you. Having it you can at least see what the various ECU's you have likely came from. He could check it out for you if it gets warm enough to remove it; no need to drive the car. He can repair almost anything in the originals but there are some aftermarket overseas sourced replacements which he cannot fix. I have the impression at least one of the ones you referred to may fall in that category. The best would be to send him the original from your car or if not one with original contents.
He did mention that the 76 and 77 Seville ECU was essentially the same except the control means for the EGR but it was something almost nobody would notice. It had something to do with both temp and vacuum as opposed to only vacuum if I recall correctly. Even other ECU's may work but the mounting brackets might be different. I've made some of the rare "large car" brackets for Bruce and he can change brackets. Anyway I will send you the list if I can figure out how to attach it.
Scott
I totally understand the "gets a little warmer outside" comment
I'm waiting for that event myself for some car work.I don't know if we can send attachments in a PM or I think they call them DM's here but I have Bruce's entire list of ECU PNs. I spoke to him and he told me I can send it to you. Having it you can at least see what the various ECU's you have likely came from. He could check it out for you if it gets warm enough to remove it; no need to drive the car. He can repair almost anything in the originals but there are some aftermarket overseas sourced replacements which he cannot fix. I have the impression at least one of the ones you referred to may fall in that category. The best would be to send him the original from your car or if not one with original contents.
He did mention that the 76 and 77 Seville ECU was essentially the same except the control means for the EGR but it was something almost nobody would notice. It had something to do with both temp and vacuum as opposed to only vacuum if I recall correctly. Even other ECU's may work but the mounting brackets might be different. I've made some of the rare "large car" brackets for Bruce and he can change brackets. Anyway I will send you the list if I can figure out how to attach it.
Scott
Scott,
That would be useful. I already sent the original ecu in as a core, though.
The one that works halfway is installed but was remanufactured by Blue Streak and I purchased that online from Rockauto, but they are out of them now, after I tried a second one, with no plan on getting more.
That would be useful. I already sent the original ecu in as a core, though.
The one that works halfway is installed but was remanufactured by Blue Streak and I purchased that online from Rockauto, but they are out of them now, after I tried a second one, with no plan on getting more.
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Duane,
Glad to hear the news! Bruce is great and always fair.
Scott
Glad to hear the news! Bruce is great and always fair.
Scott
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Somewhere I have a nice article that an owner from Australia wrote about his experience and the help Bruce provided. The same owner has a couple of my first sensors.
Scott
Scott
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