fuel injection pressure wierdness...

[rcb280z]

Here's the other thing, my cold start wont work unless the temp is 67 or colder in the garage, which it is now. I'm about 2 miles from the beach but it gets cool during the winter months here. Not cold just cool. During warmer months my Z is hard to start if it sits overnight. Have to crank it over 3 times before it finally catches. Almost like a finicky carburetor choke.

[Dave WM]

well if you ever need to replace that thermotime, get the hotter one. I think the L jettronic was used on the old super beetle VW, and IIRC that is the one I used (it came standard with the hotter temp). But like you said its really just an annoyance.

[rcb280z]

That's good info, thanks. I'll look into that.

[Dave WM]

posting up a new video shortly showing cold start/fuel pressure/thermotime etc...

 

[Dave WM]

and about 30 min later I am at 20 psi...

Oh and btw, the engine noise is really not like what is sounds like in the video. Sounded like hell on the video but in person it is much quieter. Also the fan slows down after a few seconds.

 

Edited November 30, 2016 by Dave WM

[Dave WM]

10 psi 12:15

10 psi 1:25

Edited November 30, 2016 by Dave WM

[Zed Head]

Well, that's a bummer.  I have an Airtex E8312 pump and a modified Bosch FPR and my pressure typically drops to ~25 psi then just sits there.  I've popped fuel lines on old 280Z's and ZX's that had obviously sat for a long time and found good pressure.  Clamp the lines individually and you'll know which end has the problem.

On starting difficulty in cold weather - I've found that if I crank the engine for about 5 or 6 turns then wait about 20 seconds for the fuel to vaporize the engine starts up much more easily.  If I try to get it to go by letting it crank away it seems like just a waste of battery and starter life.  I removed my CSV years ago, so it's all injector supply.  

 

[Dave WM]

I got tired of checking it after 3 hrs so for fun I wanted to see how much fuel it takes to bleed down to 0.

starter off, key on , 36 psi, key off 36psi.

push purge valve on gauge, at most 1 teaspoon of gas comes out to go to zero. I can see how even the smallest leak in the check valve/FPR/injectors could account for a fast drop in pressure.

So starting with a completely Zero pressure I reattach the fuel line, no gauge, go to start, nearly instant (just a fraction of a second), its going. I just don't get it. yesterday it was a bioch, now its fine. Maybe all the test were leaking into the intake manifold thru the injectors giving it a good rich mixture. IDK.

lets just see how it goes for the next few days.

[Dave WM]

OK its gotta be something at the pump/check valve...

went out for my nightly cruise, does not start unless I floor the pedal then all is ok. this is the same issue I had to start this thread.

I get out the pressure gauge, sure enough pressure drops of instantly AND was slow to come up. Did not notice that the 1st go around.

Clamp off the return line same thing slow at 1st then drops off as soon as I release the key from start (starter disconnected).

At 1st it would only go to about 45 psi, then I jumped to about 55 psi after a few extra seconds of START switch. After it went high on time now its holding pressure (return line still clamped). I release return line and it drops to 35psi (pump still off). There is sits and I presume will begin with the slow drop off. This sure can make you nuts.

It has to be the check valve in the pump right? Its a new pump but maybe NOS as I don't know how long it was in a Nissan warehouse before I got it.

The other thing that bothered me was the jump from 45-55 all of a sudden like. I know the pumps employ an internal bypass that seems the only thing that could account for it UNLESS I have a voltage drop at the pump terminals. I think I will get a meter out on it and have my assistant check the voltage while cranking, esp if I can get it to mess up again.

[Dave WM]

OK its gotta be something at the pump/check valve...

went out for my nightly cruise, does not start unless I floor the pedal then all is ok. this is the same issue I had to start this thread.

I get out the pressure gauge, sure enough pressure drops of instantly AND was slow to come up. Did not notice that the 1st go around.

Clamp off the return line same thing slow at 1st then drops off as soon as I release the key from start (starter disconnected).

At 1st it would only go to about 45 psi, then I jumped to about 55 psi after a few extra seconds of START switch. After it went high on time now its holding pressure (return line still clamped). I release return line and it drops to 35psi (pump still off). There is sits and I presume will begin with the slow drop off. This sure can make you nuts.

It has to be the check valve in the pump right? Its a new pump but maybe NOS as I don't know how long it was in a Nissan warehouse before I got it.

The other thing that bothered me was the jump from 45-55 all of a sudden like. I know the pumps employ an internal bypass that seems the only thing that could account for it UNLESS I have a voltage drop at the pump terminals. I think I will get a meter out on it and have my assistant check the voltage while cranking, esp if I can get it to mess up again.

[Dave WM]

another thought, maybe I should disconnect the fuel line at the inlet to the main fuel filter and flush it. That way if a piece of crap is in the fuel line maybe its just floating back and forth in between the pump and the filter? May as well replace the filter while I am at it I suppose. Think before I do that (its a year old with maybe 1000 miles on it) I not only flush the line but back flush the filter, just to see what comes out  I can both at the same time just disconnect the fuel filter, rev the direction at the hose and run the pump dumping what comes out of the filter into a jar to look at.

Edited December 2, 2016 by Dave WM

[EuroDat]

Dave, You said you check the fuel injectors on the fuel rail. So they are not leaking, but could it be a leaking csv. That could create an over rich condition that would that time to clear and get theengine to fire up.

Its not leaking at a fast amount so you wouldn't notice it undr normal driving, but standing still it could puddle and vapourise and stay in the intake until you crank it over.

You could unscrew it and do a visual check. Another thing to scratch off the list.