Power issues, misfires, lumpy running?

 

Many of the running issues are simply sensor faults, connection issues and poor set up, or a combination of all three. Now most of these have been dealt with many times here but a little known issue that is increasing with time is with relays in the fuse box that can potentially upset the clear and concise running of your zed and be the cause of all manner of issues.

 

Check out the circuit diagram above which among other things shows the fuel pump relay and the equally crucial coil pack power relay, for the purpose of this illustration the coil pack relay will be focused on but to a slightly lesser degree the fuel relay and eccs relay has the same potential issues.

 

 

 

Before delving into the “mod” I will first explain the functions of the various parts and systems in order to explain and understand the reasoning behind the theory.

 

Ok, assuming we all understand about the fuel been injected in to the cylinder and then compression of fuel and air followed by ignition spark resulting in explosion of the mixture and the power to push down the piston, exhaust stroke etc, and also assuming all is in order we can skip to the single most important part the “spark”

 

The signal starts out in the ecu, the ecu having determined when to deliver the very small millivolt signal based on information from the cas unit, tps, and temp sensor etc using the mapping details.

 

This signal arrives at the ptu (power transister unit ) or igntion amplifier, the unit`s name amplifier explains its role well, the signal from the ecu is small and does not have sufficient power handling to directly trigger the coil pack (s). So the ptu takes the smaller signal and boosts it up to provide extra electrical force ( current ) that is now delivered to the primary circuit of the coil pack.

 

Ok now quickly need to know what the coil pack does before we move on, the coil pack again is a kind of amplifier, by using a small tightly wound primary coil an electrical charge or current flow is induced ( transfered ) to the larger sized secondy winding.

 

Ok back to the plot, this now super high charge is discharged through the spark plug via the electrode tip and hence igntion spark which combined with the forces of fuel and air induction and compression of these gases results in a flame front and explosion ( of sort ) within the cylinder which forces the piston down.

 

So hopefully you all still with me at this point yes? ..................good, assuming all other inputs ( fuel, air etc ) are correct the quality of the spark will have a directly proportionate effect on the outcome of the ignition burn ( explosion) and the smoothness and velocity of the pistons downward motion.

 

If for any reason there is a malfunction in the ignition circuit such as ptu output failure, spark plug worn or insulator tracking issues then severe misfire, breakdowns or non starting can occurs.

 

This been all so obvious means that the circuit gets the attention its requires to correct the problem like replacing parts plugs, ptu etc, or cleaning connections usually to the ptu and coil pack connections.

 

But how about a fault that you do not know is there and so do not go looking to correct it??? Mmm... I see some interest again.

 

The coil packs of course have their own power supply, this needs to be switched on with the ignition and of course switched off when the ignition is then switched off. As is common with most car circuits the use of a relay is used to allow smaller current carrying circuit to safely switch a larger one, makes sense from an electrical point of view and power management point of view ( location and running of high power cable)

 

Ok nearly there now, the coil pack relay has contact in it that is used to transfer the power to the coil packs, these contacts have now been switching and carrying current for near to 20 years on some zeds and we have seen an increase in problems with the said connection.

 

Basically a bad connection will supply the coil pack with plenty enough power to run and seem to be fine, but as current demand rises the weaker connection reduces the available power to the coil packs in direct relation to demand, so having seen more relay issue arise on a hunch we have done some back to back testing and in something like 40% of cases the reduction in power supply to the coil packs via the power relay has been significant enough to warrant changing the relay,simple...well sort of.

 

In these cases mentioned the difference in the engine smoothness and response has been very noticeable despite the fact that previously they appeared to be running ok. Now I am sure we have come some way now to identifying why two different zeds with the exact same engine mods and set ups can seem so different in how they drive

 

More over although just changing the coil pack power relay has shown improvements, we have been testing a simple modification which has so far given some very encouraging results.

 

By taking the power supply switching away from the original basic relay and adding a mosfet based power supply ( regulated, clean ) and high power double pole relay for twin power and larger cables taken directly from the battery (fused ) this has made for good improvements, however by expanding the idea to include the fuel pump and ecu power relay the results have been frankly very exciting:hyper:

 

As a side note engine earthing kits have a very similar premise in that they encourage better functionality of sensors etc. but as good as they are ( maybe) they cannot increase or improve anything if issues exist in the power supplies at relay level.

 

A rolling road comparison may be a nice idea if we were a marketing company trying to sell the idea, but as I am not a fan of results from rolling roads as they in no way can mimic real driving conditions all I can say it try it, I think you will be most pleased, especially if you think your is all working ok.

 

 

Jeff TT

Very interesting, Jeff! Another great article! Are the modified relays you talk of an off-the-shelf and plug and play modification?

Very interesting, Jeff! Another great article! Are the modified relays you talk of an off-the-shelf and plug and play modification?

 

 

Thanks thats what I hope to achieve, and yes the relay upgrade is an of the shelf item the wiring and connection work neeeds some working out but not major.

 

The clean and regulated power supply can either be purchased or built as a kit if electronics is your game.

 

I am wondering if putting a kit schematic and parts required etc. together would be of any interest guys?

 

Cheers

 

Jeff

Edited June 7, 200916 yr by JeffTT

Great bit of work there Jeff, very interesting and easy to read as always :D

Thanks thats what I hope to acheive, and yes the repaly upgrade is an of the shelf item the wiring and connection work neeeds some working out but not major.

 

The clean and regulated power supply can either be purchased or built as a kit if electronics is your game.

 

I am wondering if putting a kit schematic and parts required etc. together would be of any interest guys?

 

Cheers

 

Jeff

 

Definitely - Sounds a very worthwhile preventative measure as well as cure to me!

Put me down for one!

A very interesting read Jeff and as an engine/electrics novice...very easy to read!! Thanks!

do you actually fit these items to customers z's or is it all still in the development stages at the moment.!! would be very interested in the items.

I would buy it Jeff....

JEFF you have a pm for lots of information from you regarding zedworld.

 

apologise for putting this on the thread.

Jeff are you still working on this ?

Also to back up Jeff, here are two relays from a 1990 tt one stuck now and then the other fine. As you can see from the picture both was sealed until I cut them open and know wonder it was sticking.

Humm interesting, gonna check mine out as I have an intermittent misfire somewhere

Can someone point out exactly where this relay is please :)

Large fuse box engine bay labeled ign coil, green relay

Cheers bud so would this mean I need to get one from Nissan?or do you have them jeff?

I can also show you a green relay in the same condition as the corroded as the blue one. I might be looking into this mosfet based power relay ....!

I checked mine tonight and it's fine so not my problem.

I checked mine tonight and it's fine so not my problem.

 

Are you looking for problems gaz? What makes you think it's misfiring?

Because it runs like shit for the first 2-5 mins then clears .... This happens everytime on a first cold start up.

Because it runs like shit for the first 2-5 mins then clears .... This happens everytime on a first cold start up.

 

how are your plugs and IACV?

how are your plugs and IACV?

I put some new plugs in the other week, this was part of my problem solving. Iacv I haven't tested as yet but only cleaned it a short while ago, will pull out and clean and test again

IACV may need more than a clean! There's a really good thread on here about how to test it. Try a cold start with it unplugged to see if it's any different to usual.

Thing is my idle is stable, revs up like it should when cold, comes down to a stable rpm when warm. The iacv won't cause a miss fire as far as I'm aware

That's why I suggest just unplugging as a test rather than going to the effort of a clean. It will be lumpy if it's not getting enough air when cold, and depending where your base idle is set to, you may not see any other symptoms if it's not working

I will give it a go, thanks :-)