Under Hood Fuel Pressure Gauge?

[sjpitts]

I was reading the Emergency Troubleshooting Thread and wondering if I could actually use it during a time of need. One thing that seems potentially difficult is determining if your fuel pump is working and providing fuel.

And I remembered that about 20 years ago by brother bought an FJ60 in So Cal and the sucker had multiple fuel pumps fail on the drive back to Arizona (it turned out that aftermarket fuel pumps did not work well on that car for some reason). That was a serious pain, because we were never sure what was going on.

Anyway, it reminded me that one potential cheap and easy solution is to put a little fuel pressure gauge under the hood. After my brothers experience I ended up putting one on my FJ55. I never needed to use it to diagnose a problem, but it was always there under the hood telling me that I had fuel pressure.

So would it be a good idea to install one on an 80 series for the same diagnostic reasons?

One issue is that the 80 is fuel injected, and thus has a much higher fuel pressure than my old 55. But looking on amazon there are "under hood gauges" that seem like they might work.

Like this one

A few potential issues with this plan:

First, plugging into a high pressure fuel line seems inherently problematic.

Second, I am not sure where I would install it.

Third, I am not sure if adding a pressure gauge before the regulator might reduce the pressure at the injectors-- which might be bad.

So I had another idea--- why not just install a gauge on the fuel return line-- after the regulator? It seems like you could just put a t-fitting on the return line (marked with the red arrow below). That way you are not messing with anything before the injectors. And you maybe even use a lower pressure gauge.

Now I don't think you would be able to tell your fuel pressure on a gauge installed there, but if the needle moved even just a bit you could at least tell that the fuel pump relay was working and the fuel pump was turning on, right? Wouldn't that be enough to move further down the trouble shooting list?

So tell me, on a scale of 1-10 how dumb is this idea?

Thanks

Jared

 

[Irish Reiver]

This is why my baselining/overhauling focuses on each system. Fuel system = filter, sock, pump and injectors. Buy OEM parts and there is no need for aftermarket complications. The last time those parts were new was likely 30 years ago so if they even last half of that I will be dead & gone

 

[sjpitts]

While I agree with you that a little preventive maintenance and replacement goes a long way, there is still always a chance that something will fail. Even if you preemptively replaced the critical components of your fuel system they could fail. New relays fail. New fuel pumps fail. New regulators fail.

Not very often, but it does happen.

And if you are sitting on the side of the road trying to figure out if why the thing won't start and run it seems like being able to tell if you have fuel pressure goes a long way.

But that being said, I see your point that what I am proposing may not really be worth the trouble.

 

[ppc]

Third, I am not sure if adding a pressure gauge before the regulator might reduce the pressure at the injectors-- which might be bad.

So I had another idea--- why not just install a gauge on the fuel return line-- after the regulator? It seems like you could just put a t-fitting on the return line (marked with the red arrow below). That way you are not messing with anything before the injectors. And you maybe even use a lower pressure gauge.

"Third" - Provided that you don't add restrictive fittings, adding the gauge is not going to lower the pressure to the injectors.

Pressure on the return line is meaningless. If you need to check fuel flow just briefly pull the return hose off.

So tell me, on a scale of 1-10 how dumb is this idea?

I'll give it a zero. You would adding complexity and more failure points.

 

[sjpitts]

Zero seems a little harsh, but I asked for it.

OK-- new idea

Instead of putting a pressure gauge on the return line-- how about putting a clear fuel filter or even a just a small section of clear fuel line on the return line? Again, where that red arrow is pointed.

And again, I am just wanting to be able to see if fuel is being returned to confirm that the fuel relay/fuel pump are working.

This assumes that there is some clear filter or clear fuel line out there that could be safely installed under the hood like that.

Is that idea any better?

 

[ppc]

That would be better,... may be a "3"

I just question again, added complexity, more potential failure points. Is the juice worth the squeeze for the once in ten years it will be helpful?

 

[reklund5]

You need a double length banjo bolt and appropriate fitting to install a fuel pressure gauge on the INLET side of the rail. Then you can install a gauge there. I've got a similar setup on my Supra that uses and electric sending unit to display fuel pressure on a gauge in the cabin. Useful for a boost-referenced fuel pressure regulator on a high performance setup. On a stock 80 series, its probably overkill.

Clear line on the return side won't tell you anything. There is ALWAYS fuel returning to the tank via the fuel pressure regulator. If there's no fuel in there, then you have bigger problems.

If you have fuel pressure/volume concerns, I'd baseline things with new factory Toyota parts as suggested above. New pump, sock, in-tank coupler hose, fuel filter, etc will get you sorted for the next 25 years usually. You can send the injectors out to have them cleaned/flow matched too.

 

[jht3]

i find a fuel pressure gauge very useful, one with logging even more so.

not on an 80, but on an old M3 I installed an Autometer electronic fuel pressure sender and gauge. the fuel rail is fed by rubber hose from the pump/tank, so I tee-d in a brass fitting where I screwed in the sender. gauge is in the dash. its been there for nearly 20 years with no issues. i replaced all the rubber fuel line at the same time.

i wanted to be able to check the pressure while on track, but underhood works too if you if that's all you need. a mechanical gauge would be cheaper and easier to plumb.

 

[alia176]

I think this is a fantastic troubleshooting tool to add to the arsenal. I added a schrader valve right at the fuel filter so that I can quickly attach a fuel pressure gauge then tape it to the windshield for under load conditions vs idling.