@davidf You've been through the wringer on this one! Ok, let's talk about engine sensors and sensor wiring. I'm wondering if you've got an engine speed or engine sync sensor causing the issue. If I'm not mistaken, the factory re-uses those sensors when doing a refresh, and you've obviously re-used the loom. Perhaps have a look at the loom for both of them and look for a pinched wire or other obvious issues with them. You can also quickly swap the sync (aka cam) sensor between cars (it's just a bolt in the cam cover). The speed (aka crank) sensor is more difficult to diagnose (and swap) without an oscilloscope, but I can help if you do have such a thing.
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I have seen one recently where the voltage was dropping off enough that an engine would start and die -- I think the voltage was dropping off low enough on start that it was effecting ECU/injector operation.
I keep wondering whether I have a similar issue, maybe not due to the starter motor but something else?
As John said, this one is hard work! I think you are at the point of narrowing down and working through some other problems that are not 'common' or known issues. Swapping a starter only a takes a few mins so it is something else eliminated.
Will try to get a look at the data and see if I can offer anything else.
@davidf Was wondering if you ever got your problem sorted out and figured out what it was?
@darrahc
Nothing to update on progress and problem still persists. I have had to take a break from diagnosis because of my busy race schedule, however I will update the thread once I have more information to share -- probably mid May.
I would be looking closely at grounds as well as all connections especially your main switch.
The low voltage as well as the increase in poor running you have experienced certainly leans me in the direction of loose or poor contact.
Hopefully you get a resolve soon, Rich
The saga continues ... although some progress today:
I installed the original throttle bodies that I had swapped to the good car (a couple weeks ago), set the TPS, installed the air box, fussed with the throttle cable zip ties because it looked a little close to the exhaust, and then I started it to confirm the problem still exists and ... it started right up and ran well until I shut it off. I let it warm up completely for about 5 minutes. Then I shut it off and restarted. So it is not perfect, but near perfect. The TPS value is jittery -- jumps between 4.6 and 5.3. (I had set it to 4.6 with the engine off.) It was idling at 1800 when I first started it, and now it idles around 1400 after running it 4 times.
Something is still not quite right, so I will swap the TPS sensors to see what that does. Could this be something in the throttle body that is bouncing the TPS sensor, or more likely the sensor itself?
Of note, this is the first time I put the air box back on since I installed the new engine. In my experience this should not make a difference at all, but just noting it.
Is the inlet air temp sensor in the air box? If so, was the temp sensor connected during your previous testing?
And the problem has returned. I am somewhat relieved because I need to determine the problem. I swapped in the TPS from the good car, and now it will fire up but dies after one second, which is the original symptom.
If I spray starter fluid in the air box when it is about to die, it will continue to run but will die after the starter fluid is consumed.
So clearly this is a fuel starvation issue. Maybe it is electrical which is causing the injectors to not function correctly, but I believe it must not be the spark plugs or coil; for a while (at least five minutes) the engine ran very well.
Next I will replace the fuel filter because Dan suggested it and because the car is due for a new filter. Fingers crossed this is the solution.
Is the inlet air temp sensor in the air box? If so, was the temp sensor connected during your previous testing?
Yes, the air temp sensor has been connected the entire time.
@davidf That's it. I'm out of ideas. 🙂 This has always felt like the ECU didn't know what the engine was doing. So disconnecting and reconnecting the TPS sensor might have been the fix. Or perhaps your throttles were loose and letting in too much stray air. Or something similar.
I dunno.
Keep us informed if you gather any more evidence.
Now the ECU should have enough data to point to what is going on. I would recommend downloading the ECU data and sending it to Spring Mountain.
@charleyhradicalsportscarregistry-com
will do Charley. I just collected an additional 46 second run by holding throttle. vbat starts at 10.42v, jumps to 13v while I am holding throttle, then returns to lower 12.25v when the engine finally dies. I will try to make the data widely available.
The jittery TPS sensor that I took out of the problem car runs fine in the good car and no jitter. So rule out TPS sensor.
I did not think the problem would just disappear on its own for long and I was right, but it is peculiar that after sitting for two weeks the car started and idled for about 5 minutes. I charged the rear battery just before.
@davidf spraying starting fluid will keep an engine running even if the injectors are off. So if the ecu is turning the injectors off that wouldn't necessarily indicate a fuel issue (well ok, obviously it's not getting fuel and that is an issue but perhaps not the root cause).
Do these engines have a cam position sensor? On my old race car I really struggled with an intermittent issue once where sometimes no issue and sometimes it wouldn't run. Was especially bad when the engine was warm. I'm strongly thinking this is a sensor issue and cam/crank position will definitely keep the engine from running in all of my experience (which doesn't include radical so take that with a grain of salt).
The car has a cam sensor and it is plugged in.
I swapped another main battery in this morning which I fully charged and it is a known good battery. When I turned on the master switch the volts read 11.9v. My other car is at 12.7 when I turn it on and after starting it comes right back to 12.7, and then charges to 13.2.
I am leaning more towards an electrical draw that interferes with the the ECU's ability to operate the injectors, per Dan Phillips. I never got around to swapping the starter, but I am throwing in the towel now and hauling this to a dealer (WISKO) tomorrow.
It seems to be a difficult problem. Car ran well for 7 minutes yesterday; I may of left the battery charger on during that run. I tried with the charger on today and the battery voltage moved rapidly from 11.9 to 13.2 volts (before cranking) and it ran for about 10 seconds instead of 1. That seems strange to me. The battery, freshly charged and topped off, should have been in the upper 12 volt range after I installed it.
Having seen the data and with all the symptoms you have, along with the number of parts that you have replaced, I still believe this to be a fuel pump problem.
Would also explain how the symptoms came on with the original engine, as pumps can go down, and also how this problem has not really changed with all the parts you have swapped over. Also indicated how starter fluid helps it run.
The cam sensor is working correctly,
