NB engine cuts out (not EGI relay, not cam position sensor)

93_Clubman · Postby **93_Clubman** » Tue Feb 10, 2015 11:36 am

Phil, interesting potential link between the 'blackwire' issue & the EGI (NB)/Fuel Inj (NA) relay issue. My initial response would be that seemingly the relay issue is more common on the NB in terms of causing engine depowering or not starting. Certainly the Fuel Inj relay can be an issue on the NA, but it doen't seem to result in depowering or not starting, or at least not to the same extent as NB. Of course, NA & NB may still share a common cause for issues to a greater or lesser extent with the relay.

Btw, just for sake of completeness, did a bit more searching & managed to find that while Caffeine was having EGI relay issues, the dodgy light bulb issue he was also having, was intermittent faults with the tail & brake lights: viewtopic.php?f=29&t=38526&p=535895&hilit=brake+tail#p535895

manga_blue · Postby **manga_blue** » Tue Feb 10, 2015 11:47 am

Yeah, bit of a longshot, Paul, but that thought came from reading that dumb thread about all those guys having repeated failures of their EFI relays and then blaming the relay, even when they swapped in working ones from other cars. Pretty obvious that some NBs have a wiring fault or a low resistance fault in one component that allows high current through the circuit/component (and hence through the EFI relay) without actually stopping the component from operating. A weak bridge like that across a connector terminal could do it. Hiding the bridge inside the fuel tank almost makes it malware.

93_Clubman · Postby **93_Clubman** » Tue Feb 10, 2015 12:22 pm

Totally agree Phil.
Of interest I thought from the Miataturbo.net thread, not that they addressed the cause, was that some relay internals could be tightened, & that there is a solid state version of the relay (shown along side the other version of the relay on p2). Unless this is the NB relay along side the NA relay, although the NA relays I've seen have been black instead of green.

manga_blue · Postby **manga_blue** » Tue Feb 10, 2015 12:43 pm

Yes, I noticed the solid state version too.

Might be worth keeping an eye out for one.

As far as the points misalignment in the earlier versions go it may simply be the result of dropping it or hitting it to make it work.

93_Clubman · Postby **93_Clubman** » Tue Feb 10, 2015 3:18 pm

manga_blue wrote:Yes, I noticed the solid state version too. Might be worth keeping an eye out for one.

Indeed - so just did a bit of looking & noticed posts 17 & 18 in following, in which the SS relay only lasted minutes in slightly modified MX5s: http://forum.miata.net/vb/showthread.php?t=546182
May be ok in standard car.

Garry · Postby **Garry** » Tue Feb 10, 2015 7:07 pm

Does the EGI relay really power the fuel pump? What does the fuel pump relay do?

manga_blue · Postby **manga_blue** » Tue Feb 10, 2015 8:15 pm

Good thinking. The EGI relay feeds the high current side of the fuel pump relay. So if the fuel pump or its connectors are the culprit then both EFI and Fuel Pump relays could be warm.

luzinit · Postby **luzinit** » Wed Feb 11, 2015 9:13 am

Solid state relays are not worth trying if you're having issues with OEM relays blowing. I bought two and both died after a week or so.

luzinit · Postby **luzinit** » Wed Feb 11, 2015 9:14 am

To add to that, they were approximately 45 bucks shipped from the states. I bought two by accident... OEM ones can be bought from your dealer for around $30.

irwin83r · Postby **irwin83r** » Mon Feb 23, 2015 12:07 pm

have you put this one to bed american?

have you got a friend able to lend you a working cam angle sensor from their car?

i have read of and have had issues with cam angle sensors failing once hot even when new.. got lucky with one or two just being poor connections (hence the cable ties) but my problem has returned and after borrowing a friends cam angle sensor yesterday the problem went away totally.
so perhaps to be certain take a spare next time you are going to get it warmed up and do a swap?

The American · Postby **The American** » Mon Feb 23, 2015 2:06 pm

The cam and crank position sensors have both been swapped for new ones ( earlier in this thread). I have not solved it, but current theory it is the current draw from the Walbro 450 lph fuel pump that has just gone in. My theory is the additional load is overheating the main relay causing it to fail. It then cools and the car can restart.

The pump was changed from a 255lph unit when the car was set up for e85.

aviper4u · Postby **aviper4u** » Tue Feb 24, 2015 9:01 pm

The American wrote:The cam and crank position sensors have both been swapped for new ones ( earlier in this thread). I have not solved it, but current theory it is the current draw from the Walbro 450 lph fuel pump that has just gone in. My theory is the additional load is overheating the main relay causing it to fail. It then cools and the car can restart.

The pump was changed from a 255lph unit when the car was set up for e85.

so according to the above the problem will go away OR atleast lesson durung the cooler months?

Magpie · Postby **Magpie** » Tue Feb 24, 2015 9:07 pm

No it won't if the relay is overheating because of current draw then you need:
1. Reduce current draw
2. Heat sink the relay (difficult)
3. Replace relay with one suited to the draw
4. Rewire fuel circuit with solid state relay and wiring matched to the draw.

The American · Postby **The American** » Tue Feb 24, 2015 10:43 pm

Magpie wrote:No it won't if the relay is overheating because of current draw then you need:
1. Reduce current draw
2. Heat sink the relay (difficult)
3. Replace relay with one suited to the draw
4. Rewire fuel circuit with solid state relay and wiring matched to the draw.

Thanks magpie,
Perhaps:
1. Revert to the 255lph pump (require check that it keeps up with fuel demand)
2. Have thought about this and read about others doing this with a CPU fan -not attractive to me
3. & 4. This is the option I think I'll look at - replace with a more substantial relay and wiring.

C-Gazer · Postby **C-Gazer** » Wed Feb 25, 2015 12:56 am

Hi American,
I thought I might try to offer some advice concerning relays. The EGI relay should have a good 12V on its coil when energised . Without the full 12V the coil will not close the relay contacts closed firmly. Hook some light wires to the relay coil base to see what volts you are getting.
When relay contacts close they are supposed to be adjusted so they wipe together not just close . What is the condition of the relay contacts are they burnt have you tried cleaning them? In my experience relays generally overheat when there is high resistance connection between the relay base connections especially with large currents.
Something you could try is to leave the cover off the EGI relay and when the engine stops in fault condition leave the key on and confirm the relay is still energised (contacts closed) . Good luck with the fault finding ---- C-Gazer