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The SA has lost most power, misfiring, and occasionally running completely fine when not doing the first part. While compression is low it was consistent (cheap HF compression tester (with shrader valve)), I don't suspect the engine to be at blame. This led me to running through the free items first:
cleaned carb (weber 48 ida), ultrasonic machine and disassembled (ran as it is before and after);
looked into timing, seems to be within spec;
haven't touched ignition yet but everything appears fine;
I considered the cat was clogged but I tested that by going open header (no change, well stupid loud);
Air and spark are fine... leaving fuel.
I decided to drop the tank and look instead of just replacing the fuel filter because I suspected if the tank was bad I'd need to replace the filter again so better check the tank. It could also be an intermittent fuel pump but if it's intermittent then it'll be hard for me to verify, I an also hear it inside the car and I don't recall a difference in sound. Anyway, I dropped the tank. While collecting the fuel into gas containers, I didn't notice any debris and the inside of the tank appears fine. I've also never seen a bad tank. What did cause some alarm was the what appears to be paint spray or something. I tried to look at the ceiling of the tank with a mirror and again looked the same, grey.
Considering the fuel poured out clear and the little that's left in the tank I've splashed around trying to find something. I suspect it's not the tank? I'm going to replace the filter regardless, actually right after this post.
What should I check next? Go back to stock ignition? Replace the fuel pump? Pull the engine time?
Oh yeah, my drive way is a hill so test driving isn't fun at ALL. It barely makes the power to climb the hill.
Should I go ahead and get the tank cleaned/sealed even if it is fine?
What are the other details of your fuel system.
Sounds like you might be running an aftermarket fuel pump and regulator? Where is the filter located relative to the tank and pump?
I would look at the filter and pump. Sounds really strange, if it has proper fuel pressure and idles well its odd it cant even get up a hill.
Last edited by tommyeflight89; 03-30-22 at 06:45 PM.
D'oh! I should have added that.. it is aftermarket, Holley red, IIRC. and there is a return style regulator. I did notice that the pressure would read low or zero after a drive. I know that happens when the gauge gets warm. I didn't make it to replace the filter yet but I'll do that soon and have more information. I do have a sight-glass on the carb and it's always looked full but I know it doesn't take much to fill it back up.
My fuel gauge is also off shows 3/4 while full and works it way down from there. SA and FB gauge senders appear to be different but the electronics are the same? At least, that was my quick cursory search. Right? I figure while I'm in there.
My experience with fuel issues on a weber IDA on a 13B race prepped engine was it would be fine below ~4000 rpm, and would be fine on 1/2 throttle or less, it was really only once it got to WOT at some speed it sounded like hitting a rev limiter. The issue we had was a small piece of plastic from the packing of the carb getting jammed in the fuel delivery tube of one rotor. Really through us for a loop.
Can you explain a bit more of what your misfire/power is like? Is it across the spectrum of of RMP/speed/load? How intermittent is it, or is it relatively consistent?
Have you double and triple checked your ignition timing/wiring is correct? We have also had that problem where it would idle with totally incorrect plug wiring but would not drive...
I agree with others - cheapest thing is to replace the filter. When i bought my original RX7, it had "fuel delivery issues" and the filter looked spotless but as soon as I replaced that, it ran perfectly and is still driving on that engine. Generally speaking, i replace the filter every spring just cuz. I'd start there and report back before chasing other stuff especially if you can see fuel in the float bowl.
not sure what is easier, so this list isn't really organized
Ignition:
check the wires, a new wire is like 8K Ohms, the max allowable is 16k Ohms, it will misfire at 16k
have a look at the cap and rotor, they are wear parts
would not hurt to put a timing light on each wire and make sure you have leading and trailing.
Fuel:
find a container with some kind of measurement on the side, mine is supposed to be for juice. it needs to be 1 liter, ideally 2.
put the fuel hose in the container, and get your stopwatch out. if you have a 1 liter can, you do 30 second tests, if its 2 liters you can do a full minute.
a stock fuel pump will do more than 1400cc a minute. if it doesn't you will have problems.
1. Put a "T" in the fuel line that feeds the carb(s)
2. Run a line to a cheap handheld fuel pressure gauge
3. Tape the fuel pressure gauge to the windshield so that you can read it while driving
4. Put the car through its paces, to include high RPM and extended load
If the fuel pressure drops below the recommended value for your carbs, then you know to hunt for fueling issues. If not, there's some other problem.
Minor update: rebuilt the Mallory Comp 70 pump and after rebuilding it backwards (pumping air into the tank. I installed the gerotor housing 180 degrees out) then figuring out that having air in the fuel line won't allow the regulator to operate. I'm finally getting pressure to the carb. I stopped afterwards as it was getting late and I need to do a full inspection of every system I touched to ensure bolts and nuts are torqued and so on. I also wanted to check that the ignition is in spec (because it's easy to do and why not). I should have a final update soon. Provided nothing else comes up.
Unfortunately, I'm not going to make it to DGRR this year despite being only an hour or so away. Double booked and too busy
Yep, still won't start.. gets close but no cigar. Its interesting that both the fuel pump and the ignition coils went out over the winter down time. Could this be a sign that the alternator (S4 alt, 70amp IIRC) is over taxed?
I was having some hot start issues on HOT days that I assumed was vapor lock from deadheading. I installed a return-style regulator and that seemed to make better but I didn't have a lot of seat time afterwards. The radiator fan is setup to turn on low when at 195f and high at 210f. If air conditioning is on then high anytime the rpm is under 1100 (I think it is, where ever the stock aircon idle adjust relay dictates.) The fan is a dual speed Ford Contour (IIRC). My ignition coils are MSD Blaster High Vibration Part # 8222, which I found out have lower ohm values than a lot of the other coils I've seen.
@t_g_farrell your assumptions were correct. I reversed removed DLIDFIS and car started better than it has in a while. My guess is both ignition modules died together. I'd like to understand what happened as I'd rather have DLIDFIS but I'm not dying to switch back. The car fine great for a while but I started noticing it would occasionally break up in the higher RPMs I'd say over year or so ago. Then I started having hot start issues and I figured that was vapor lock so I solved for that. This past winter before I stored the car for winter it'd break up in the mornings but it wasn't consistent or easily reproduceable. Eventually it wouldn't start..
Should I try going back to DLIDFIS? I did have a heat sink but the modules still got fairly hot.. That's the only thing I see as maybe an issue. Can the distributor signal be too dirty and cause issues? or an ignition coil pull too much juice? or go bad and wreck the modules? I did have the replace a bad coil. MSD 8222.
03-30-22, 05:07 PM
Fuel tank opinion
Double booked and too busy 