chaseincats

This is kind of my fault because I didn't explain the scenario that got me to where I am (since I was so positive it was a fuel pressure issue). I was driving when one of the fuel hoses in the back of the car (that I later learned was quite old) blew. The car lost power as expected since it wasn't getting the amount of fuel it needed due to the split hose. Looking on my AFR gauge on the dash, it went from 14.7 on the highway to 19, and was sputtering with no power. After trying the accelerator a few times with no improvement, I put it in neutral and killed the engine - coasting to a stop in a CVS parking lot. I turned the car on and it was front firing a lot - turning around I noticed a massive puddle of fuel spraying out from under the car - I turned it off immediately and called a tow truck. After getting the car home, I put it up on jack stands and changed the split hose (the only one I didn't change a year ago for some reason, go figure). The hose that I replaced hung a bit low (like I was talking about at the beginning of the thread) so I zip tied it up. I turned the car on and it was sputtering and front firing and later discovered that I zip tied it too high/tight and kinked the hose. After cutting the zip tie and re-hanging it, we were back to the 32psi we've been chatting about. Long story short, the car was running great in its current setup until a fuel line blew, causing it to do quite a bit of front firing on the highway, parking lot, and home when looking into the hose kink. I've heard front firing can damage the AFM, which is the only reason I keep talking about front fire. I can richen the car with the AFM (or the potentiometer) but that isn't solving the problem since it was running fine with the current configuration until this event with the fuel hose and the running lean/front firing as a result of the split hose only allowing a fraction of the fuel needed to keep a proper AFR entering the engine. I hope that makes sense @Zed Head?

Arg. Looks like I’ve hit a dead end with the fuel pressure then? Any suggestions on where to look? The car was front firing a lot when the fuel line blew and it ran very lean. Could the AFM been damaged by that?

I have some fuel pressure numbers for you. When I connected a fuel pressure gauge between the fuel pump and dampener in the rear of the car, I got 40 with the key off but pump on, and 34 with the car running with 32 psi reaching the front with the fpr vacuum tube on. Is 34psi out of the pump's fuel outlet while running correct?

It does but that makes me curious why it originally sat and idled at 36 psi before I messed with the hoses.

In the past, my idle was at 36 with the vacuum line connected but now its 30 and the car is running lean. I believe the FSM says it should idle at 36 too.

This is not an ignition/efi/jetronic/TPS/sunspots/etc issue. The car was tuned-up to factory spec with the ET chapter of the FSM and using the AFR gauge a couple years ago. This problem started immediately after the hose changes (the post-installation test drive) whereas the drive before changing the hose was perfect ("rocket mode"). AFR readings: - before hose change: idle 14.2, cruise 14.7, WOT 12.5 - after hose change (with FPR vacuum line connected): idle 14.7, cruise 16-19ish, WOT 13.7 - after hose change (with FPR vacuum line dis-connected): idle 16.9, cruise 15ish, WOT 12.8

Since the pressure gauge is in the engine bay (spliced between the fuel filter and fuel rail) I wouldn’t be able to do that but I can monitor the engine in real time with my AFR gauge if that helps. In the past I’ve always spliced the fuel pressure gauge in that location so my past reading sand this are from the same location.

Aftermarket - this one

Just to be sure I'm not barking up the wrong tree with blockages/restrictions - the pump wouldn't be the issue right? Since it's an electric pump it will either work or it won't and not become weaker, correct? The pump is probably a year old

Ok so here's some more information from tonight's festivities: - I think the original issue wasn't the height of the hose, it was that I had it zip tied too tight (kinked like @Captain Obvious suspected). I turned the car on and had someone watch the fuel pressure gauge in the engine while I wiggled the hoses from all angles/pulled it as high up under the car as I could, and it didn't change - which is why I think it was kinked - With the car turned on we're still sitting at ~30 psi at idle with the vacuum hose connected to the fpr and 38psi with it unplugged, idling, with my finger over the hose to prevent the vacuum leak. I just took the car around the block and it is incredibly sluggish (acceleration sits in the 15-17 range on the air fuel ratio gauge). I pulled over and unplugged the fpr vacuum hose and with 38 psi, the car is a rocket again - so the gauge fuel pressure gauge is right there definitely is a fuel pressure issue here...

Nah, the only things I replaced were my 20 year old hoses

Thanks! This is interesting and I'll tell you why. The car ran horribly after I replaced the old tank-to-pump hose (due to age) and I eventually found that I had 20psi coming out of the fuel pump due to me zip tying the tank-to-pump hose higher than where it had been before being changed. After lowering the hose (to a couple inches over the half shaft where it had been i believe) I saw my psi go up to 32. The car used to run great before I replaced the hose so I must not be hanging it right as it idled at 36psi. Long story short, I don't understand how these pumps are able to spit out 36psi when routed that high compared to how I had it.

Hi gang, Could someone take a picture of how the hose that connects the tank to the fuel pump is routed on a 77/78? Mine has always sort of hung under the car suspended over the half-shafts with various zip ties which isn't right.

Gotcha - thanks

I'm going to re-foam (and as a result re-cover) my seats and am looking for a duplicate of what is already on there which the PO installed but I can't seem to find them. I contacted thezstore and this color combination isn't something they've ever sold. Does anyone know where I can find a new duplicate of these?:

I took every hose and the vapor tank out and tried to blow in one end while keeping the exits plugged and none of them had a leak which is what's so frustrating about all of this. Any idea where the check valve is under the car that goes from the tank to the engine bay?

This is definitely a gasoline smell rather than exhaust. I sealed all exhaust inlets using a smoke machine and shop vac. If you blow in the line in the engine bay that heads to the vapor tank and scamper back there, you can smell fuel coming out of the area inside the hatch near the vapor tank even though I've changed the hoses

No, it was me thinking that hooking up the carbon canister in the engine would pull fuel vapors out of the vapor tank since replacing the hoses/pressure testing everything back there seemed to show no leaks.

I smell gas in the rear of the car on the inside - coming from the vapor tank area. I pressure tested the tank then all hoses and none of them had a leak after I replaced them - but I still will periodically get a fuel smell in the cabin anyway. Hooking up the carbon canister (the hose was open since I got the car) was my idea to fix the issue because I thought vacuum was pulled through the canister to pull fuel vapors out of the vapor tank but I now know that isn't how it works 😞.

Got it - ok that makes more sense, sorry. I originally had the hose just open in the engine bay but never smelled any vapors coming from it - only from the rear of the car in the cabin. Could my check valve between the vapor tank and carbon canister be bad? I can blow hard into the line in the engine bay and sometimes smell gas inside the cabin even after changing the hoses (but it got considerably more difficult after changing them).

Sorry if I'm not explaining this properly. The purge line is connected where the vacuum actuator line used to connect (the t-fitting by the throttle body) - for the idle vacuum leak reason. The purge hose is larger than the hose used for the old vacuum actuator line (which isn't in use now and replaced by the purge hose) so I have a larger t-fitting and had to heat the smaller hose ends to fit on the t-fitting. Does that make sense? I can make a video if that would help?

This might be a stupid idea but I’m going to ask it anyway haha. Could I connect the ported vacuum line on the throttle body to the vapor tank hard line to have the fumes sucked out as I drive?

Gotcha, that makes sense. I ended up hooking the carbon canister back up assuming (wrongly it seems) that the vacuum would suck the fuel vapors out of the tank instead of having them continue to leak into the cabin (despite changing the hoses). What I ended up doing was pulling the cap off the vacuum valve and plugging the large purge hose directly into the top nipple (since the valve doesn't hold vacuum), and connecting the purge hose to the T-connector allowing vapors to be sucked in through the throttlebody inlet. I don't understand why it wasn't done that way to begin with since it's still going into the intake manifold through the throttlebody as you press the pedal... That said, it sounds like the canister doesn't really pull vacuum from the vapor tank so that idea won't fix the issue. It's odd because I only smell fuel in the cabin sporadically - I'd have thought if there was a hose leak, I'd smell it all the time. Have you encountered this?

Right, but I’m not hearing any thing being pulled from the tank-side hose of the canister when off idle when I put the hose up to my ear

So I ended up hooking my carbon canister back up but noticed the amount of vacuum going into the canister from the engine is not the same level of vacuum going from the canister to the tank. I pulled the vacuum line off that goes into the canister and pressed the throttle body accelerator arm and put my ear to that hose and it was considerably louder than when I put my ear to the hose that comes out of the canister (the one that heads to the vapor tank). Is my canister plugged or is that how this is supposed to work to not pull full vacuum to the vapor tank?