curly

iTrader: (25)

Used but new to us? Does that work? I'm convinced anything off of a '90 is junk. It all rusts and locks up much worse than my '93. Mazda definitely perfected their rust inhibitor paint in '93, then proceeded to let the accountants build the '94+.

greddygalant

iTrader: (3)

Sitrep. Replaced the FPR with another working one and the symptoms continue. What to do next gents?

rleete

iTrader: (21)

After rereading the thread, it seems to me to be a fuel enrichment issue. The clamping the line but no change part has me baffled.

Something with the throttle body?

miata2fast

iTrader: (2)

I am suspicious of sensor issues. I predict the ECU always thinks the engine is warm.

curly

iTrader: (25)

Well it wasn't the worst waste at $15.

The idle is high, 1000-1100 when warm. I'm guessing the iac and warmup valve isn't functioning at 100%. But no amount, little or big, of throttle input changes how well it starts.

Why are we not blaming the fuel pump again?

curly

iTrader: (25)

Sensor was checked, it has values very close to the FSM. Only reason they weren't exact is my "cold" wasn't exactly 60* and my "warm" wasn't exactly 160* or whatever they list.

I could take it out and test it in a joe Perez manner with a thermometer in the water while testing resistance. However I feel like it would be a waste of time with initial tests pointing towards good numbers for the thermosensor and poor numbers for the fuel pump.

rleete

iTrader: (21)

Any resolution to this?

Godless Commie

iTrader: (2)

Because starting up an internal combustion engine is not a taxing affair for a fuel pump.
Pretty much any engine will sputter and catch on a couple drops of fuel.
That is to say, if you had a problem with your fuel pump, it would make itself a whole lot more apparent when it is needed - under load/elevated rpms.

hornetball

iTrader: (4)

+1

curly

iTrader: (25)

Nope. We replaced the FPR with a supposedly tested used unit and the problem remains. We haven't done anything else with it as of yet.

I know the two idle valves are almost definitely not working properly, it seems to (finally) start at a steady 850rpm when cold (when it should warm up closer to 1500rpm) then once warm it idles happily at 1100rpm (too high), which is with the idle screw closed completely.

williams805

iTrader: (2)

Any sort of fuel leak will cause extended cranking after the car sits for a while (hot or cold). This means internal leaks too.

The fuel pump has a check valve in it that should hold fuel pressure after shutting the car off. If it is bleeding the fuel back into the tank it will allow air into the lines. When you try to start the engine after this, it has to bleed itself before it will run properly.

To see if you have a leak, hook your fuel pressure gauge up. Get the car running for a while to make sure the lines are full of fuel. Shut the car off and leave the gauge hooked up. Watch the gauge to see if all or most of the pressure bleeds off. This may not happen right away depending on how large the leak is. May take ten minutes or two hours. Just check periodically.

If it is pressure goes down close to zero, diagnosis it straight forward.
1) With gauge still attached, get the car running again for a while to purge lines.
2) Clamp both feed and return lines and turn the car off all at the same time. Make sure the gauge is in between the clamps.
If the gauge bleeds off like this, you either have an external leak (between the clamps) or a leaking fuel injector(s). If it does not bleed off ,again give this plenty of time, move to next step.
3) Remove one of the other clamps and watch for bleed down. If it doesn't bleed down...
4) Remove the other clamp.
If when removing the regulator side clamp it bleeds down, the regulator is at fault.*
If when removing the feed line clamp it bleeds down, the fuel pump is at fault.*
*Make sure there are not external leaks in between the clamp in fuel tank.

Hope this helps.

curly

iTrader: (25)

Sounds like a legitimate cause. Wouldn't it go away when I jumped FP and GND for a minute or so before starting? Pretty sure I've done it with the return line clamped as well.

I'd love to do the above test, but the HF gauge I was borrowing leaks pretty bad. It was showing good pressures, but I'm not sure I'd trust it for a leak down test for obvious reasons.

And by "fuel tank leak", I'm guessing you mean the check valve by the FP is bad?

williams805

iTrader: (2)

It does seem to me that running the fuel pump for a minute first would rule a leak out. I didn't see that part.

chpmnsws6

iTrader: (12)

If it was the FP leaking down, it'd just have a little extended start period. Half the XJ's on the road take 3-4 seconds to start because of this. You can cycle the key a time or two befor you start it to keep from cranking. I don't miss that POS.

curly

iTrader: (25)

It's all very confusing and frustrating. And of course greddygalant and I are flipping this miata, and it's at his house now with a dead battery with the charger at my house. So testing is on hold until he borrows the charger. For now it still drives awesome, pulls hard, it's just the starting when cold that's annoying. I'm trying to think how one of the idle valves malfunctioning would cause it to crank long, but if they were stuck open, it would just start at a really high idle. If they were stuck closed, a little throttle input would help. And it doesn't.