Car won't start - But relays are good

Technical and Repair Discussions
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PostPosted: Mon Mar 15, 2021 3:44 pm
JBPDXOR wrote:Kurt,
You can buy a crankshaft sensor online for $9.00 up to $28. I would just shotgun and replace. Even if the problem is not solved you will have an important spare part.

Part # BE8Z-6C315-A

Sounds good. Thanks!
Kurt Breitinger
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Chassis 494
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PostPosted: Thu Mar 18, 2021 4:59 pm
If the car won't turn over I don't think it's at the point where the crank sensor would be an issue.

I'd suggest connecting a laptop to the ECU with PE3 software running and make sure all the sensors are showing valid values (especially voltage.) See what happens when you press the starter button. If voltage doesn't drop much and starter just clicks, it's likely a solenoid; if voltage drops a lot, then it's likely the battery or starter motor. Or, as I mentioned earlier, a hot lead or ground connection that's bad.

BTW, using the PE3 software is the best way to diagnose a bad crank sensor (it will show up in the graphs)

If you have a couple of friends and some pushing space, you can try an old-fashioned push jump-start (in 2nd gear). That will generally uncover if it's a starter/solenoid issue (our go-to at-the-track solution), something we did quite regularly with the initial batch of starters.

BTW. the ECU's do go bad at times...
Bob Breton - SRF 51 - San Francisco Region

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PostPosted: Fri Mar 19, 2021 1:06 pm
Thanks Bob,

Using the PE was something I did not know or think about.
Using the PE Viewer makes a "world of sense".
Wow, I now know how to evaluate sensors plus monitor Lambda 1 & Lambda STF.

We recently had a very hard time trying to start JD's SRF3. We used numerous methods to start the car. Nothing worked. The motor would just barely turnover. Took the starter a AB&E electric and it tested great.
The short answer... replaced the battery. Starts.
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PostPosted: Mon Mar 22, 2021 12:29 pm
Glad to hear it turned out to be the least expensive option! One lesson I've learned is that once you've over-discharged these small batteries they are pretty much junk even when the voltage looks good (need those amps for starting!) Forgetting to turn off the master is the #1 offense.
Bob Breton - SRF 51 - San Francisco Region
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PostPosted: Mon Mar 22, 2021 9:54 pm
breton wrote:If the car won't turn over I don't think it's at the point where the crank sensor would be an issue.

I'd suggest connecting a laptop to the ECU with PE3 software running and make sure all the sensors are showing valid values (especially voltage.) See what happens when you press the starter button. If voltage doesn't drop much and starter just clicks, it's likely a solenoid; if voltage drops a lot, then it's likely the battery or starter motor. Or, as I mentioned earlier, a hot lead or ground connection that's bad.

BTW, using the PE3 software is the best way to diagnose a bad crank sensor (it will show up in the graphs)

If you have a couple of friends and some pushing space, you can try an old-fashioned push jump-start (in 2nd gear). That will generally uncover if it's a starter/solenoid issue (our go-to at-the-track solution), something we did quite regularly with the initial batch of starters.
BTW. the ECU's do go bad at times...
Well, it's not the starter or the crank sensor. I've replaced both. Kevin at Comprent was pretty sure it was the starter. I just turned on the PE3 software, but didn't know what to look at. I didn't leave the engine power on for very long though, because I didn't want to fry the relays. They just keep clicking real fast. When I hit the starter button, the screen goes dark and the relays quit clicking. Does that mean anything to you?
Kurt Breitinger
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Chassis 494
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PostPosted: Tue Mar 23, 2021 2:02 pm
Once you drop voltage below about 11.5 volts, the ECU won't stay powered-on, so that would shut everything down, including the relays.

Were you able to successfully connect the PE3 software to the ECU by selecting the "Direct" option on startup? If successful, ou should get a confirmation dialog box showing an IP address (and a green confirmation in the lower-right corner of the screen). If you don't see a display of ECU data, select "Display" on the top menu, then "Engine Data". If that doesn't show "Battery", you can right-click to select the pulldown next to any Position, and scroll down to select "Battery". With the ignition switch on you should hopefully have good battery voltage. You should also see a valid water temp. If you want to confirm if you're actually "live", move the throttle pedal to see if the "TPS" value changes (if that's on the screen.) There indicator at the bottom left of the screen should also be "green" ("red" indicates you're not connected.)

I'm not sure what you by the "screen goes dark"? Are you referring to the PE3 software, or a car dash? If the PE3 software loses connection, you should see "Offline" in red in the lower left corner of the main PE2 window.

I'd still recommend putting a standard volt-meter on the battery to see if you get a big voltage drop on a start attempt (and initial ignition switch activation). If the relays are cycling open/closed (clicking) there just may not be enough voltage/amps to keep them closed. E.g. can you hear the fuel pump when you turn on the ignition switch? Have to tried swapping the Fuel & Master relays (or replacing them?)

One item missed on a recent engine change was connecting the chassis ground to the transmission. That's definitely a requirement (and also a problem with the connection at the frame that needed to wire-brushed to clean up the ground connection; same at the battery to frame ground).

Master switches and their connections have also been sources of bad connections. Also, the occasional "short" to ground.

I'm a big fan of dielectric grease on any electrical connection (learned early from experience with the Gen2 harness and rain!)
Bob Breton - SRF 51 - San Francisco Region
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PostPosted: Thu Mar 25, 2021 6:35 pm
Well Bob, in the end it was the battery. The voltage appeared to be good, but not enough amps to start. The weird thing is that it came without warning, like a street car might give us.
Kurt Breitinger
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Chassis 494
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PostPosted: Wed Mar 31, 2021 8:55 pm
Good new, Kurt. These batteries can take a "dump" with little warning. Biggest cause is leaving the Master switch on enough to draw down below 11v; they may recover on recharge, but definitely won't help the starting, especially in the Gen3 where low voltage can cause the ECU connection to drop out. When it's off-season, it's a good idea to disconnect the ground in the case there's some residual current draw (I've seen this happened when the master switch is not wired correctly or someone's bypassed the master entirely by adding on an ancillary circuit for data acquistion, for example.) Keeping batteries on a battery tender helps, too.
Bob Breton - SRF 51 - San Francisco Region
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