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

[bruce]

Did u buy a new relay? Is notthe same spec as tthen old one?

[bruce]

R any new additions tapped onto the 12v feed of the egi relay? Thus overloading it and heating it up.

[93_Clubman]

irwin83r mentioned his NB8A cam angle sensor plug used to work itself loose once it got hot - he secured it by puting a cable tie around it - still ok years later:
viewtopic.php?f=19&t=23453&p=299175&hilit=cable+tie#p299175

tachometer drops to zero immediately even while the engine is still turning.

Tacho zeroing is interesting - on NAs this tends to happen with dodgy coilpack/s, but of course NB8B has a different arrangement regarding coilpacks, ie coilpack is built into two of the four sparkplug leads, like coil on plug (CoP). And the NB8B plug leads tend to be pretty reliable.

So it might be time to have a look at your ECU, as timk mentions tacho gets signal from the ECU on the NB:
viewtopic.php?f=81&t=52554&p=662156&hilit=tacho#p662156

[Mr Morlock]

american- it was the comment that tapping it made me think it was the culprit. Recently a friend had some probs with an MX5 same model as mine and I also noticed that the EGI was hot but it was also hot on my car- maybe they are all hot after driving for some time ?? I will defer to the experts.

[bruce]

Wet ecu? Might be worth removing the carpet/cover to see if all dry and clean.

[luzinit]

I have had the same issue with EGI relays failing and potentially due to heat, the electromagnet gets weak. Swapping a new relay in just masks the problem until such time that the new relay also fails. A new relay would last me 1day to 3months and I've gone through 5 relays in the last 12months.

A lot of things have been mentioned in this thread but its likely that more current is flowing through than the relay than acceptable, causing it to overheat and fail.

Finding out what's causing it is the tricky part. In my car I've cleaned and checked all ground points, checked bulb connectors and any faulty bulbs. Checked wiring and pins under fuse box. The issue still persisted.

Recently I changed the coil pack and a new relay. Relay still gets hot so I'm not sure if I've fixed the problem. That being said, I touched the relay on a nb8b which had no problems and whilst it was hot, wasn't too hot to touch like mine.

One thing I haven't checked is the ECU.

Good luck. I will report back if I can survive a few months without blowing another relay.

[The American]

The fault has occurred with two separate EGI relays, both of which got very hot. The ecu is clean and dry. Connection fault causing resistance and heat, or excessive current draw. Or perhaps both.

Here's a shot of the original relay and its contacts:

[The American]

This is the original relay. I noticed that the contacts that you can see on the right were misaligned, so much so that the leading edge of the movable contact was meeting the contact on the coil in the middle on its edge. That could be a heat source?

That does not explain the failure of the replacement which appears reasonably well aligned.

[The American]

I also noticed that one of the four male terminals on the underside of the relay had no significant score marks from the female terminals in the fuse box. I've tighened up the female terminals.

I also 'Adjusted' the moving contact to realign is with the stationary one, reassembled it and installed it. The car starts and runs. Now I'll have to wait for my next free hot afternoon to see what happens.

Luznit - have you seen the posts about people who've installed auxiliary relays to take the load off the factory one? If my issue ends up being about current draw for legitimate reasons, I will look at that.

[The American]

Bruce,
I think the power for the fuel pump and ecu come through the EGI relay (someone correct me if not), so it might be that these are a source of extra load. I don't know how to test that theory.

[luzinit]

I have read about it people installing auxillary relays, I'll try and dig up the post tomorrow.

In my case the car is stock other than an upgraded fuel pump, alarm and headunit. The issue happened a while after headunit and alarm were installed and well before my fuel pump was installed, so I don't think its those items.

[manga_blue]

The EGI relay powers the ECU, fuel pump, coilpacks, fuel injectors and all the engine sensors. If the EGI relay is getting hot it's most likely because of excess current flowing through it. So potentially one of those components has an earth leak. Feeling for extra heat in each of those components might find it, at least before the whole engine warms up too much.

Otherwise can you borrow a temp gun?

http://www.jaycar.com.au/productView.as ... rm=KEYWORD

[The American]

Not a bad thread on the topic (from Miataturbo): http://www.miataturbo.net/engine-performance-56/help-car-died-fuel-pump-not-priming-solved-main-relay-64489/

[The American]

Manga, that's a handy suggestion. I don't have a heat sensor, so finger sensor will do the first pass!

[manga_blue]

Not a bad thread on the topic (from Miataturbo): http://www.miataturbo.net/engine-performance-56/help-car-died-fuel-pump-not-priming-solved-main-relay-64489/

I don't think much of that thread. Everyone seems to be blaming the relays, even when they swap in new ones. No one is thinking that it's something else downstream causing the relays to fail.

Also worth checking for a loose wire in the harnesses touching earth intermittently.

Also have a look at what I found about metal particles bridging the terminals inside the fuel pump. That would do it too. Have you been buying cheap/dirty fuel? viewtopic.php?f=55&t=46425&p=822568&hilit=pump#p822568