inconsistent starting

[lglade]

I'm with RRoller123. I think vapor locking is more likely a phenomena on the low pressure side of a fuel pump; the pump can't suck fuel from the tank because of the vapor bubble. But any vapor in the fuel rail (which is on the high pressure side of the pump) should just get pushed through the return line back to the tank.

If it's a borrowed/rented fuel gauge that's reading so low, then I'd be inclined to get a different one and see what results you get.

[micbrody]

I think pump is fine. It sounds the same; I also removed CSI and replaced with a hose to gas can to see if fuel was being delivered to fuel rail. Turned on pump and immediately it filled the extra tube and quickly drained to gas can.

I am thinking (and hoping) that low pressure is just odd behavior related to a lot of air in fuel rail/injectors.
What I cannot conceptualize is how air would cause the pressure regulator to not allow pressure to build up much at all. Everything worked fine before disassembly. With air, I would think most air would immediately be flushed; but any residual air would be pressurized with fuel to a total pressure of 38. The only way I can see regulator not working is from debree lodged at diaphragm keeping it open. But maybe air can cause problem.....

In any event, I will re-install rail and injectors to engine and fire up. If no luck, I will check fuel pressure; if still low, then I will have hook pressure gauge to outflow of pump; if that reads normal , then only thing I can see is that pressure regulator not working.
If it turns out to be flaky pressure regulator, that would explain the bad intermittent starts

[micbrody]

replaced the gaskets on fuel injectors Large and small. Went to re-install. I could not get fatter gasket into bigger hole. (maybe if I had engine out I could). I took off large new gaskets to replace with older large gaskets............and when removing my LAST large gasket, the screwdriver slipped and cracked off the ceramic head of fuel injector.
So now at a standstill.

Do I buy new fuel injectors? or just one? (I assume they need to be "pressure matched" (same flow rates when clean)
Anyone have extra fuel injectors they would sell?
Anyone know of new ones to use that work well?


Vicks has these: http://www.vickauto.com/newstore/index. ... ts_id=3727
midwest:www.midwest-bayless.com/c-56-fuel-injec ... 4SC-0.aspx

[micbrody]

I guess I just broke the "pintle" cap. I think I can replace it. Any help would be apprecitated

[micbrody]

I read that pintle cap is "over-rated"; and that many people don't bother replacing immediately. So in the interim, I will proceed and contemplate injector replacement or repair at a later date.

So I re-installed fuel rail and plugs. It started right away. I then shut down; re-installed pressure gauge and started. Car started, but pressure went from 0 to 38 over the course of at least 15-30 seconds. I would have expected it to climb to 38 within 1-3 seconds.
I then turned off car; let it sit overnight. Over the the first 4 hours, pressure dropped from 38 to 30. By morning it was at 10. I tried to start car; but difficult. Took me over 30 seconds to start; and pressure gauge remains at 0 when car running. Engine accelerates fine and smoothly (granted, note with car moving , so little load)

So I am really confused. Is pressure gauge randomly not working? or is there truly little pressure in fuel rail. I would think with tiny fuel pressure, that MAYBE idle would be ok; but acceleration.

I am starting to think that maybe my fuel pump is flakey? but why can I smoothly go to 4000 RPM. Or it could still be a pressure regulator that is intermittently working.
One last thing I tried with engine running: (assuming I did not reverse installation of two engine bay fuel lines. When I slowly manually clamp fuel feed to rale, the engine slowly conks out. If I slowly clamp the fuel return from the fuel pressire regulator, the engine slightly accelerates (no change from zero on pressure gauge) ; but as I make restrictionore severe, the engine conks out . This, I think, suggests a fuel delivery issue (bad fuel pump, that can only deliver fuel at very low pressure). But if bad fuel pump , should I still be able to deliver fuel to accelerate to no load 4000
RPMs?

As a bonus discovery, I think I noticed two small coolant leaks: steam coming from some point in radiator (very very tiny ). And tiny seepage from top of engine

[bluespider262]

I had a rust clogged sock inside my tank and the symptoms were similar to yours. Started and ran usually, but sometimes not, and would hit a brick wall at certain RPM/speed.

Before you dive into a spare pump, experiment with bypassing the Fiat's fuel tank, using a gas can temporarily, and see if the pressure is better. You should hit full PSI pretty much instantaneously of that pump coming on, not 30-60 seconds for sure. If not that pretty much leaves the pump or regulator but your regular sounds okay.

[124JOE]

good point i had a pickup sock that was black cloged and brittle
it wasnt hard to change out

[micbrody]

A clogged line is definitely a possibility. However, this repair adventure began by trying to cure inconsistent starting; not running. I have never had RPM problems once the car starts; or under load going 50mph.


I do have original gas tank; when gas level low, I took sender off and looked inside. Looks fairly clean; not sure where sock is located or how to replace (1981 Fi ).
I think (regardless of eventual cure) I will add a fuel line screen (not a fine filter) from tank to pump, to catch any potential large pieces of "gunk" that could ruin pump. Any suggestions as to what to use for screen?

Today's mission: today I will replace the soft fuel lines that go from pump to filter; and filter to hard line. While doing that, I will try to rule out newly clogged filter or bad pump

[courtenay]

Others might correct me if I'm wrong here, but I think that if you put a screen between the tank and pump, and the screen clogs up and stops the flow of fuel to the pump, the pump will burn out as it is cooled by the fuel flowing through it.

[micbrody]

The screen I was talking about was a porous one; one that would stop a fairly large enough piece of debree that would damage pump. I would imagine that when it would get clogged enough to reduce flow , it would immediately be noticed by sudden performance issue. I would then immediately check screen and clean vs buy new pump.

[micbrody]

I replaced fuel pump with Bosch from amazon.com "Bosch 69133 Original Equipment Replacement Electric Fuel Pump". $70 delivered.
Bosch automotive web site says its compatible with Fiat 1981 Fi.

Pump very quiet; and though only one day, the car has started immediately 5 times, and comes to 900-1100 Rpms within 1 second.

I believe problem is solved.

[124JOE]

thats great i hope you have many years of trouble free driving ahead