Black Smoke

[zed4ps]

I have recently changed my 260 to a l28 injected motor. i have had the motor and head reconed now when i get the car started it blows black smoke ,runs rough and won`t start when warm.  Have fitted fuel injection fuel pump as well as surge tank new fuel regulator and am running out of ideas, any help would be great. Cheers Peter.

[Scoota G]

Sounds like excess fuel pressure. What figures are you running?

 

[zed4ps]

Have no idea , how do i test? cheers Peter. Thanks for the reply

[Scoota G]

Should be a blank plug on the fuel regulator to hook up a gauge. I think L28 fuel pressure for efi is mid 30 psi. Can anyone confirm this?

[C.A.R.]

F/Pressure wants to be between 40 - 60psi.

[zed4ps]

Cheers , i`ll check it out.

 

[Zeddophile]

One or two other things to look at, makes sure your air flow meter and coolant temp sensor are plugged in.  And make sure the flap on the air flow meter isn't stuck - if a flapper air flow meter gets backfired though, it can bend the shaft the flap pivots on, and jam in one position.

 

F/Pressure wants to be between 40 - 60psi.

 

Lurch, not trying to be a smartass here, but are you sure about that?  I thought from memory that L-jet systems should normally run 2.5 bar, which would be 36 psi under load, and obviously a bit lower at idle.  60 psi is 4 bar, that's up into modern diesel supply pump territory....    You haven't by any chance been thinking of oil pressure figures, or something like that?

[Zedman240®]

Fuel pressure in alot of EFI cars is around the mid 30's PSI, Bosch K? or L-tronic run at higher pressures like 70 80ish from memory. Diesels are in the thousands.

[Zeddophile]

Fuel pressure in alot of EFI cars is around the mid 30's PSI, Bosch K? or L-tronic run at higher pressures like 70 80ish from memory. Diesels are in the thousands.

 

Maybe K-jet is 70-80, I haven't dealt with that system at all...  After posting in this thread, I looked in the '280zx revs up in Park' thread, and someone there has quoted the manual as saying 250kpa (36psi) for the 280zx system. 

 

Diesels are in the thousands after the mechanical high pressure pump, but a lot of modern diesels use an electric pump in tank to supply the high pressure pump at 4 bar (or a bit more).  Same as direct injection petrol engines actually, the fuel system in those is very similar - electric pump supplying around 4-5 bar up to a high pressure pump, which is often run off a camshaft.

[pauly_adams]

38psi is the correct pressure but from 35-40 psi there is not a great difference in fuel deliverey

[C.A.R.]

Yes it appears I was a incorrect with my statement...

 

In any case, does the OP not  have a workshop manual?

[PZG302]

I have a 280ZX fuel injection manual on PDF, if you can give me an e-mail address I can send you a copy of the book.

[zed4ps]

pddl4@bigpond.com              Thanks, Peter

[dat2kman]

And, if you get rid of the standard pre set fuel pressure reg/return to tank off the rail thing, replace it with a adjustable one ie Malpasi, you can get it giving you the oressure it needs, and accurately, using a decent inline guage running off a Tee, with the engine at various throttle psitions.

Lurch was right, the stock pump, will produce between 40 to 60 psi in pulse, but the L-Jetronis system needs to be regulated to an even 35 to 40.

Problem is the stock press regulator gets tired, and allows it to pulse, thus over fueling the odd injector or two.

 

To OP, get a decent ie 4" diam fuel pressure guage tee'd in, and run the engine, at various rpm's see what she is doing, compared to the settings as per the manual that pzg302 is sending.

[PZG302]

and the manual is on its way through the magic of the interwebs

[funzies]

Had a similar problem when the rb20 was put in my car, turns out the fuel return line was too small causing massive back pressure.

[pauly_adams]

the other thing i would try is, open your fuel cap find the return line coming from your fuel rail and blast it with some compressed air. mine was blocked once and would not start at all, my fuel pump is a fair bit bigger also, so it may just cause yours to run rich

[Scoota G]

and the manual is on its way through the magic of the interwebs

Another Happy customer. Well Done