by "Chairman Kaga" (mike-mckinnon)
Published 04/12/2017 at 11:40
by "Chairman Kaga" (mike-mckinnon)
Published 04/12/2017 at 11:40
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STARS: 1
Let’s say you, or someone, accidentally mixed up the fuel send and return lines while replacing the hoses, and tried to start the car a few times before you, I mean they, had realized what they’d done. Then let’s say that car began experiencing a number of issues, like erratic and inconsistent fuel pressure and vacuum readings, to the point that it no longer ran.
Do you think maybe that fuel hose mixup wrecked the FPR? My understanding of the part’s guts is that there’s a check valve that actually regulates the flow of fuel back to the tank and thus maintains consistent fuel pressure, but gets opened more or less by a spring/diaphragm that’s actuated by vacuum depending on injector duration/ignition. So it’s not as if the reverse flow would LIKELY put undue stress on the diaphragm. It’s confirmed there’s no fuel leaking from the vacuum port. However, could the valve have been damaged or weakened? And that sometimes it works and sometimes it doesn’t? Fuel pump is brand new, no hose leaks, no injector leaks. My friend isn’t sure what else it could be.
"RacingShark" (racingshark)
04/12/2017 at 12:04, STARS: 1
That’s about the only thing I would think you could mess up.
Had a friend do this on a miata. Other than frustrating the crap out of him for hours, no damage was done. I suppose it depends on the car.
"ITA97, now with more Jag @ opposite-lock.com" (ita97)
04/12/2017 at 12:54, STARS: 0
The FPR would be about the only thing that would be at risk of damage. I actually did this myself during the KLZE swap on my old MX6. When I got everything buttoned up, it took me a few minutes to figure out why it wouldn’t start.
"Chairman Kaga" (mike-mckinnon)
04/12/2017 at 13:02, STARS: 0
Well, I’m replacing it because I can’t find anything else that it could be, even though the diaphragm isn’t leaking gas. I mean, my friend is.
"just-a-scratch" (just-a-scratch)
04/12/2017 at 13:06, STARS: 0
Were the hoses and fuel pressure regulator reconfigured before the engine ran erratically, with inconsistent fuel pressure?
If no, go fix that first.
Was fuel pressure applied to the air/vacuum side of the diaphragm?
If yes, it’s possible to have fuel trapped in some part of the regulator and causing trouble, or simply to have over stressed some part of the diaphragm.
"Chairman Kaga" (mike-mckinnon)
04/12/2017 at 13:17, STARS: 0
This car has had so many issues that I honestly can’t say.
But no, the fuel hose was never connected to the vacuum port. The hoses were mis-connected at the hardlines at the back of the car, to the send pushed up the return line, and vice versa. The worst that could have happened was fuel at full pressure (35-36psi in this car) was forced the wrong way into the return valve. Now, since that valve is not designed to keep gas out, but rather let it in, maybe the spring was damaged? That’s the only idea I have, short of pulling the entire fuel system and shipping the injectors off for testing. At this point, and given the age, I’d probably just replace them. Every other component in the system is new. Pump, hoses, rail, etc.
"just-a-scratch" (just-a-scratch)
04/12/2017 at 15:17, STARS: 0
I doubt undue stress on the diaphragm is a cause here.
Let’s say your regulator is set to 35 psi. If you put only 28 psig on the fuel side that enters the regulator, I would expect the valve to stay shut.
With some tees, a manual valve, a gauge, and a bucket, you might be able to do a simple pressure test on the regulator. Connect the gauge between the regulator and pressure source (pump, fuel rail, etc.) and put a manual valve to bleed down pressure somewhere else upstream. Route the discharges of the manual valve and regulator to a bucket. turn the pump on with the manual valve closed. Slowly open the manual valve and watch the pressure when the regulator stops flowing. If that pressure is below what your injectors need, you have a problem with the regulator.
I haven’t tried the above myself. So, it might not work as well as I imagine. Anyway don’t blow yourself up or catch on fire.
With all the extra fittings and stuff it would take, there may be an easier way. Like, maybe, just buy a new regulator.
"Chairman Kaga" (mike-mckinnon)
04/12/2017 at 17:29, STARS: 0
Yeah. I’m choosing Option B. Worst case scenario I’m out a few bills and end up with a working spare, which is never a bad idea when you own an Alfa Romeo.
"gmporschenut also a fan of hondas" (gmporschenut)
04/12/2017 at 21:16, STARS: 0
what kind of car?
A lot of older cars had a charcoal canister. If the vacuum lines get swapped, you’ll get no flow to the engine. I know for 914s if the canister is reversed it can get jammed and needs to be replaced.
"Chairman Kaga" (mike-mckinnon)
04/13/2017 at 10:07, STARS: 0
‘82 Alfa GTV6. The model didn’t get the canister until ‘84. The plenum plumbing was changed pretty drastically that year, too.
I did remember that maybe around the time this started I installed a new distributor rotor, as mine was cracked. It was a different piece, supposedly the correct piece from an actual Alfa parts supplier, but I also know the distributor changed in ‘84 as well, replacing the old-style vacuum retard with a vacuum advance. I just wonder if MAYBE I didn’t get the correct rotor and that’s causing the problem? Let’s be clear - I really don’t believe that a piece of bakelite with a copper bit on the end will cause the kinds of problems I’m having, but I’ll pull the old part (it’s still usable) and give it a whirl.
If I can get the car to idle long enough I’ll recheck the timing. Might as well check the cam timing too. Maybe the belt slipped and that’s causing a loss of vacuum, which is causing the FPR to misbehave as well as just run like crap.
I dunno.