blazer1313

First things first. I thought the fuel pressure to the rail connected to the rail and hit the FPR first. Mine is hooked up so the fuel hits it last. So it hooks up so it hits the fuel pulsation dampener, #1, #2 injectors then the regulator. Is this correct? In any case I hooked it up to both lines and the line that went to the dampener first (I take it its the pressure line), when i turned on the key it was only at 32lbs. I started it and it hit 39-40lbs. Revved it it hit 45lbs. WAY TOO LOW. I know I'm supposed to have anywhere from 50 to 71lbs. Before I replace my fuel pump I should check my inline fuel screens in side the fuel pump itself correct? But would this prohibit 10-30lbs of pressure? If I find nothing in the screens and have to replace the pump should I go with another new stock pump or upgrade to the Walbro 255? They're about the same price. Yes I have a '84 N/A 13B engine but I want to do a turbo swap later anyways. I plan on getting an aftermarket FPR with guage no matter what. Another question....when I hook up my new FPR should it be located on the pressure side before the rail or after on the return...still kinda confused. Plz respond ASAP. Thanks!!!!!

Nate

LongDuck

Okay - first off, slow down in your descriptions and take your time. It's hard to determine if you've got it hooked up in the correct fashion which will definitely affect fuel pressures at high and low.

Fuel flow diagram is as follows

Tank->Filter->Pump->PD(rear)->Feed Line->Rail->PD->Inj1->Inj2->FPR->Return Line->Tank

Keep in mind that the FPR is on the end of the rail nearest the rear of the car. PD is nearer the front. This operates to increase fuel pressure by shunting off flow of fuel at the rear of the rail, effectively increasing pressure at each injector 'upstream'. The FPR is vacuum actuated, so you'll want to be sure that your vacuum system is working correctly that leads to the FPR. You also have a Pulsation Dampner at the pump - these are mounted in pairs to reduce 'hammer-effect' of fluid in a line.

The stock pump is good for a 2 injector system. Filter contamination will cause drops in fuel pressure at high and low settings. The 'screens' that you're taking about on the pump are not usually user-serviceable, but could also account for a drop in fuel pressure. A crimped fuel line or cracked fuel lines (old) could also cause a drop in pressure, but you'd smell this right away.

And lastly - why are you checking fuel pressure readings? Is your car not running correctly and you're trying to troubleshoot something?

Reply back when you get a chance,

gsl-se addict

iTrader: (3)

Nate,

You have the fuel pressure gauge connected correctly. The fuel pressure regulator is the last part of the fuel rail before the fuel goes back to the tank. The FPR uses a diaphram and spring to regulate pressure. When the pressure is high enough to push the diaphram in, the outlet of the fuel rail opens up, relieving the excess pressure. This is how the FPR regulates fuel pressure. There is also a vacuum line connected to the back of the FPR that connects to manifold vacuum (after passing through the solenoid with the orange connector). This makes it so the fuel pressure changes with manifold vacuum. This is done so that the pressure difference between the fuel and the manifold (where the fuel is injected into) remains constant.

As far as you readings go, they are high if anything. Connected the way that you have it, the fuel pressure should read about 28 psi at idle and should bump up to about 37 psi when power is placed to the orange solenoid (the orange solenoid causes the FPR to reference atmospheric pressure instead of mainifold vacuum, thereby increasing fuel pressure).

The 50-70 psi that you mention is directly from the pump. To test this, disconnect the portion of the fuel pressure tester the goes to the engine. Take this line and block it off with a bolt or something. Turn the key to the 'ON' position and either prop open the AFM door or use a jumper wire to connect the two terminals in the connector with the rubber boot next to the AFM. This will cause the fuel pump to run with the engine off. You should be in the 50-70 psi range (my is about 60 psi).

If you are not in this range, you could have a bad fuel pump, clogged fuel filter, or a bad FPR on the pump (there is a FPR on the pump besides the one on the rail).

So don't go out and buy a pump yet. See what further testing will tell you before you just start replacing stuff.

Kent

blazer1313

I later remembered that this low number was the fuel pressure with the FPR. And yes it is a bit high. I will need to borrow the kit again to test the pressure from the pump.

And yes there is a drivability problem

#1 There is little change in acceleration after half throttle all the way to the floor. I believe its starving for gas. What I do know: TPS is adjusted properly ignition timing and components are great. Fuel filter is great. Air filter is great.

#2 My injectors are leaking, both of them. I have already bought 2 sets of injector o rings and grommets. Removed the plastic spacer between "block" and injector rail bracket that is used mostly in the 86-91 models. I have the air bleeds at the bottom.

I think its a little strange that when I upgraded to the RB header, RB Presilencer, RB lightweight steel flywheel, SPEC stage 3 clutch, removed air pump, removed ACV that I would notice a big difference and I haven't yet.

What do you guys think?
Nate

Rx-7Doctor

iTrader: (13)

If you back out of the throttle and slowly accelerate does it pick up speed? rx7doctor

blazer1313

just to middle throttle then accelerates slowly after that

blazer1313

a little help?

blazer1313

^

LongDuck

Seeing your bumps and not finding a definitive solution to the problem, I would suggest that you remove the intake piping (from AFM to TB) and look at the TB butterflies as you operate the throttle linkage. You might want to have someone inside the car press the accelerator so you can see what's really happening.

What you're describing almost sounds like you have an airflow obstruction that prevents the right amount of air from getting into the engine. If the TB appears to be working correctly (diaphragm choke butterflies open at cold), then the TB is probably fine. Next, I would look at the AFM.

The airbox can be removed from the AFM by the 4x12mm bolts at the bottom of the airbox. The AFM vane should move freely through it's entire travel and if it's binding for any reason, this would definitely affect fuel flow to the engine, affecting it's ability to rev to higher RPM's.

Have a look at these and then reply back. Any other recent work that you've performed or any other problems that might seem unrelated?


Hey, was reading another thread and this was posted by "SAtwentytwo" and might be helpful to you:

"...catalytic onverters and fuel filters have similar warning signs, they both will make you bog down, but a cat that is going out wont cause a stumble like that...catalytic converter problems are most notable on accel, when you full throttle into it it feels like your running out of engine, you wont get full rpms or full power, and usually it will act like a rev limiter is on, but if you ease into the throttle you will think nothing is wrong (most of the time unless its a severe cat meltdown). fuel filters tend more to buck at cruising speeds, but then again with as old as our cars are, its Not wise to buy a cheap 5 dollar filter...with all the rust and contaminants in the fuel tank, you may do more harm than good by putting in a cheap filter that may not filter anything. also check your carb, my fuel bowl appears to be leaking and i belive that is where hard starts and bucking is coming from. also when your car is running take a can of carb cleaner and spray your vacuum lines down. if you notice a bog in rpms, you have some vacuum leaks to deal with as well that could cause the same problem...I work as a Tech for GM, and i figured maybe id go a little more in depth than the other guys about what could be wrong, just covering all the bases. hopefully its something easy and cheap though good luck"

blazer1313

Finally tested my fuel pump. It's kicking out 64psi. So thats out of the question unless it can't pump volume... few more things to test. I adjusted TPS a while ago with ohm meters and with the "listen for the click" methods and ran great. Just bought some 12V DC lights and I'm going to wire up a two light TPS "analyzer". All in all I found I need to replace some crakcing but not leaking rubber fuel lines. My FPR is running 2psi high, the screens in my fuel pump "might" be clogged but the aren't user friendly to take out and clean. And I have to still test my AFM and ignitors. Sigh*

blazer1313

just tested TPS with new 12V light setup. As I suspected. Already adjusted correctly. Great $4 gadjet that will help out a lot of SE owners around my area though.

LongDuck

Those 'cracking' rubber fuel feed and return lines are likely because they're for carb'ed fuel systems, and aren't "Fuel Injection Hose" which will be printed in white letters on fuel injection-specific tubing. If you're not positive that these are the right Fuel Injection Tubing, it was a good move to take the time to replace those hoses now before they sprung a leak and start spraying fuel around in there.

Where the injection system sits, any seepage that you have (or spraying) is right above the hot exhaust manifold or header, and will quickly lead to a Car-B-Que.

The FPR is probably fine - more pressure will only lead to slightly higher fuel consumption, but at cruise and steady state throttle, the CPU will use the O2 signal to tune this correctly. Fuel pump screens are a possibility, but I've never heard of anyone on here replacing those or cleaning them out. I've never done it myself.

AFM check is simple - remove A/F and use your finger or stick a pencil (eraser end) in there and make sure that the AFM door moves smoothly back and forth - if it's catching anywhere, that could be a potential cause. Ignitor test is to swap them and see if anything changes. If the car won't run after the swap, it's likely the trailing ignitor was bad (moved to your leading ignition).

Keep at it, you're ruling stuff out. HTH,

gsl-se addict

iTrader: (3)

What about your 5th/6th ports? Are they working? If they are stuck or if the tube that goes from the LIM to the exhaust is removed or damaged (maybe didn't get hooked up with the RB exhaust?), you will see a significant loss of power on the top end.

Other typical causes of this problem are clogged cats (you don't have any), clogged fuel filter, or bad fuel pump (not enough volume).

I would check the 5/6 ports first, then check into the fuel pump volume.

Kent

blazer1313

i can feel them open at 4K. I can manually moven them freely. Air injection tube is OK due to inspecting it when replacing cat with RB presilencer. One more thing. The previous owner lost the air filter top, ya know the plastic cover. So my air filter came and is still zip tied into the air filter assembly. Just wondering if its starving for air due to air isnt directed from in front of the radiator into the AFM or is this not an issue?

smnc

You're STILL having injector leaking problems?
DUDE!!!

We've gone through EVERYTHING...


And no, taking off the top off the stock box would only INCREASE the airflow...

I assume your engine compression is good?

It doesn't sound like fuel starvation to me. That tends to feel more like a stumble or 'miss', especially at high revs under load...

Rx-7Doctor

iTrader: (13)

If your injectors are still leaking at the rail you could be pushing air with the fuel
Need to get them sealed properly. Are they leaking at the top from the rail or at the bottom where they go into the housing.
You don't need to remove the ignitors to do swap. just switch connectors and coil wire posistion. First check to make sure you have the coil wires hooked up properly. rx7doctor

blazer1313

hmmmmmm


can see fuel running all over the orange part. so most likely from o rings (already replaced twice with vasoline). I'm going to see if i can find some larger o rings that will still fit inside the rail..

smnc

I had a thought.

You could send you current injectors out for cleaning and leak testing and cleaning/flow balancing.

Might let you know if there is a problem with the injectors themselves...