74 1.8 - fuel pressure regulator?, opinions. Options

[wonkipop]

car = 74 1.8 L jet (all intact).

problem =
out driving this morning - gradual then worse loss of power. no accelerator response.
pulled over. cut out. no idle. let it sit for a few minutes. restarted it. got it going.
got up road all right, but symptoms kept coming back, then going away. limped it home.
fun ruined for driving, but fun diagnosing started.

felt like your classic fuel starvation.

background. car has been recommissioned and back on road for about 5 months.
running beautifully.
fuel system entirely rebuilt. clean tank. new fuel lines. new fuel pump. new injectors.
all vacuum lines renewed. all ignition compenents renewed. except coil (which could be original, looks like it, but coil was tested and was a goody).

one thing = fuel smell in engine bay on lhs around air cleaner. comes after a few days sitting. had put this down to saturated charcoal cannister, feeding back fumes into aircleaner. have inspected all fuel lines etc thoroughly and no signs of any external fuel leaks/wetness. just a vapour smell thats not there all the time, just after sitting.

pulled everything apart today down there after getting home today.
checked everything. all tight, no air leaks. no bad hoses.

looked at pressure regulator. which sits right there under aircleaner.
i have no reason to think its not original and about 45+ years old.
and did not get replaced. looks great externally, but.........internally?

will get car into shop this week. where i can get some guages on it etc.
at home with car. nothing but basic tools.

but whats thoughts out there.
anyone had this one before.

[timothy_nd28]

Okay so if I understand correctly, we have two conditions here: car dies randomly after warmed up, and a idle hunt?

I wouldn't eliminate the fuel delivery system just yet, it can be dropping out intermittently from the contacts inside the AFM or dual relay. Where is the fuel pump located in your car?

You replaced the fuel injectors, what did you replace them with? I suspect a lean condition or too much advance on the dizzy that might be causing the hunt. You need to verify timing again, and it might be time to invest or borrow an air fuel ratio gauge to see where we are at.

[wonkipop]

Okay so if I understand correctly, we have two conditions here: car dies randomly after warmed up, and a idle hunt?

I wouldn't eliminate the fuel delivery system just yet, it can be dropping out intermittently from the contacts inside the AFM or dual relay. Where is the fuel pump located in your car?

You replaced the fuel injectors, what did you replace them with? I suspect a lean condition or too much advance on the dizzy that might be causing the hunt. You need to verify timing again, and it might be time to invest or borrow an air fuel ratio gauge to see where we are at.

i will take it out for big test drive today to workshop to see if it can be induced driving.

will be resetting dist and timing there - we fiddled with it on monday.
doing a check of the ECU plug and relays AAmeter CHT sensor etc..
have an L jet diagnostics manual now and the EFI circuit diagram.
will finish what i started to be 100% sure.
i know all the mech parts of the fuel system are delivering, so a fault if still there, is probably in the controls as you say.

got the gear, air fuel ratio guages, even exhaust gas analyser out at workshop.

one of our members here has kindly offered to send me down a new cone gasket for the throttle body from brisbane. very nice of him and communication was unexpected. members here look out for each other even in this far off corner.

i see 914 rubber make this valuable little part.

i realise its time to get a spare of all the EFI components in a box. one of each.
have noticed there are real difficulties obtaining an AAvalve.

i'll confirm what i think was going on after today.
the longish drive to the workshop followed by a shutdown and restart roughly 10-20 minutes later will either confirm it was the throttle body and cone gasket or it is a gremlin still in there. if the fault persists i seem to have found a way to induce it and test while its faulting if it comes back. but even a repeat late last night of the start up exercise seemed to have indicated its gone. touch wood.

injectors were replaced with a set of bosch injectors (still sealed in plastic bags and boxes with nozzle caps) i bought last year. from a vw guy in colorado. original correct parts. injectors are good, we tested them before install about 9 months ago.

the cold start injector was not replaced, it was working, but its on my list today to take a look at it and ensure its not leaking.

the fuel pump is located in the under engine position up under the chassis rail spot (factory 74). i don't think its vapour lock, or collapsing lines, checked all that on monday. been running the car for 7-8 months now and on hotter days and for longer distances than for what has been going on now without problems when driving. the pump is new. the only sign of vapour lock is occasionally after shut down it takes longer to crank for restarting. but it does not, not start, on the first crank. usually start is immediate, but on those occasions it can be 5-6 seconds of cranking to fire.

we know we are getting fuel down the lines from the tank with good flow, pulled them off to check just to be sure when we did the pressure flow test on monday. checked the return line.

to be clear, the car does not die randomly. it died during the first episode of the "condition". when this first appeared on sunday it was during driving. the throttle was hesitate and the engine failed to deliver power and rev cleanly, i pulled to the side of the road and was giving it the gas to try and keep the engine going, it died as it came down from revs, or failed to settle at idle. it restarted straight away. and drove. but did it twice more before i got it home. one thing i'll say for L jet, it tries real hard to make the engine run even when it does not want to.

i'll know more after today.

it looked to me yesterday like the throttle body was in the early stages of working itself off the plenum. one of the screws took a quarter turn. the body was 1 mm further out on one side than the other. normally i would not have thought that was a problem as for all intents and purposes it was "tight". i think with a cone gasket in good "as new" condition it would have been sealed. i'm guessing that at certain times it was sealing and at other phases of thermal expansion it was opening up. i'd had it all apart about 9 months ago during recommission and had put it all back together carefully then. seating it evenly. so it had definitely moved since then. not by much but it had moved. i'll know more when i take the gasket out, which i don't want to do until i have the replacement to go straight in.