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I would not worry about whether your handheld vacuum pump maintains vacuum when connected to port on the FPR, too many places you can get leakages that are not related to a problem in the FPR. If the diaphram is ruptured in the FPR, I am pretty sure you will see fuel spitting out of that vacuum port on the FPR when the engine is running. 


My Aeromotive FPR does not hold pressure when I shut the pump off. Its not an issue and I see it as a safety feature with no high pressure fuel in the lines / injectors when the engine is not running. 

With the engine running does the fuel pressure change when the hose connected to vacuum port on the FPR is removed?

Is the line connected to the FPR vacuum port rigid plastic?
If that line and the others connected to the throttle are rigid plastic, they could very well be brittle or cracked with age / heat. Check each one and consider having those replaced.

Speed-Pro are now know as FAST. You could contact them to see if you can get the latest software / instructions.

Damn it. Yes item #6 in the link below and also #2. So I probably should hook the vacuum hose up again to the FPR, start the engine and observe the PSI when I take the hose off. If it keeps running at that point then attach a clear hose onto the FPR vacuum port and exit it to the rear of the car just to be safe & see if I get any trickle of gas when running the car for a few minutes.

Areomotive Q & A

Finally got back to it.  I did three things as shown on the attached paper:

Header temps: With temp gun aimed on the headers I know the temp gun may not be all that accurate because of distance & various things, but I took the temp of all headers before starting and they were all pretty close to equal. Then after a few minutes of running most headers were around in the 500 - 800 range but the one as shown was only 150. So maybe something is up with that cylinder, spark plug or whatever. 

FPR: I removed the vac hose from the FPR and the fuel PSI went from about 41 to 48. Also no gas came out of the FPR even after warm up. 

Engine Vacuum: Hooked up my mighty vac to the engine vac hose and did a video which showed at idle a bit bouncy vac at around 12, then I gave it a little steady gas pedal which made it bounce around more, then I followed with a small quick rev at the end which made the vac go quickly from 12 to 8 then 18 then 10 and then back to 12. Will try and add the video seperate, only 22MB but it won't load yet. Still can't load the video but basically its as noted above.



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Last edited by does200

If you are only seeing 150 degrees on the #8 cylinder, then you are either flooding that cylinder with fuel or you don't have any spark there. You could also not be putting any fuel into that cylinder, which could indicate a clogged or defective injector. Either way it would appear that you are only running on seven cylinders. Have you done a compression check on this engine?


Thanks. Yes next step would be to take a look at that cylinder plug after all cools tomorrow. I had them all out a couple months ago to try and fix this erratic running and will check my photos since I numbered all the plug photos. No, never did a compression check on the engine, but all was great till a few months ago. Here is that video I mentioned above. I have a stethoscope listening device so I suppose I could climb in there and listen to that injector and see if it sounds different than a few of the others. I try and just do a little here & there since its in the garage with fumes (door open and fans help a little).


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Last edited by does200

You have to compare it to the others plugs
Knowing how to "read" a plug requires a lot of experience and I only have a little but it seems very black and greasy, it is certainly not worn but it is not beautiful in any case and shows although this cylinder malfunctions.
A badly functioning cylinder + the fuel pressure which immediately drops to 0, I continue to bet on the leaking injector # 8.

Thanks guys. I found a place with the same spark plug, so I'm on the way to get that and try it out. The plug basically looks the same as all the other plugs that I pulled out & cleaned a couple months ago (although back then they all had a little more black film on them due to not being changed in years). About 10 years ago my fuel injection guy said he tuned the car to be a little rich so I wasn't really surprised with darker plug endings when I checked them all & cleaned a couple months ago. But who knows, I will know for sure when I get a new clean plug in. As far as testing a faulty injector, all I know how to do is to maybe listen with my stethoscope on the injector or maybe also feel the injector to see if the feel or noise is any different than the others, no? Probably will pick up a new plug wire too in case I want to be sure the wire to that plug isn't faulty. Although that will be a pain in the crotch to try and reach back there without going in the other way by the seats.

Last edited by does200

The app3923 might just be the platinum version of the copper plug you have. The thread and reach is the same according to their website. Take your plug along with you to the store and check the tip to the base of the washer is the same. 
It will be ok to run the car for a short while with the one odd plug but you would need to get a new set of what you had originally. They also need to be adjusted / replaced more often than platinum or iridium plugs. 
Your plug looks fouled but you need to pull your other plugs to compare. 
You could move #8 plug to a different cylinder and see what result you get before buying a plug. 
If your new plug fouls / cylinder does not get to temp, then do a compression test or leak down test. 

Got the new (same 3932) plug into the engine where the lower temp header is and it still runs rough. Then listened with my stethoscope tool on the fuel injector on the left side of engine and on the right side of engine and did the same listening on the left & right heads. But each side sounded the same. I might pick up one of these spark plug wire testers in the link below just to be sure I have spark through the wire. Probably next step is to find my compression tester and do a check. Its around somewhere because I did my old Maserati Biturbo years ago. I did another quick header temp test and the one was still lower than all the others. I wonder if some of that may just be the header being closer to the engine bay opening & has more circulation to fresh air and therefore may just normally have less temp than the others. Right side did the same with lower temp near the engine bay header although not as noticeable as the left side variance. Next time I pull out my other Panteras I'm going to check the header temps. I still think its too much heat variance though.

Spark plug wire tester





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@bdud posted:

rene4406 look at the link I posted in my reply earlier and does200’s link to Aeromotive faq’s. These regulators are not designed to hold pressure with key off. 

Ok i hadn't read it all

But this plug does not have a satisfactory appearance and we do not test the injectors by listening to them, even with a stethoscope, we dismantle the rail, we feed the pump and we check that none is leaking and then we make them charge all at the same time in identical and transparent containers and we check if they have all delivered the same quantity.

Check the compression is also a good thing.


Yeah I agree the plug looks kinda dark which I suppose should really be kind of a light tan color but then all the plugs were like that in Dec. If its rich, maybe its not due to excess fuel but instead limited air? The FI company first inclination was the valves in the throttle body could be the culprit. It appears easy enough to take a stack off and see if anything looks odd especially for that one cylinder, although I suppose that could be a longshot. I suppose I could also put my hand on top of each individual stack and see if there is any change in engine sound (spitballin here). As you say the stethoscope didn't prove anything either but at least nothing sounded different from engine side to side on the fuel injector, head or valve cover so at least the fuel injector is clicking. In looking at how to do the compression test on that one cylinder I don't really feel like taking all the plugs out again, finding the fuel fuse, disconnecting the coil. I thought I could just hook up the gauge to that one cylinder and turn it over 3 cranks prior to start and read the gauge.

Ha ha yeah "ancient" and "no experience" is me. But at least I'm not the average Ferrari owner and would just tow it in. Pantera guys are a bit different. I'm not ruling anything out as the cause, and even on the FPR Areomotive link above it says its normal for the FPR to not hold vacuum when testing at vacuum port with a hand held vacuum pump because its normal for some leakage to occur at the pressure adjustment screw threads. So I may try some silicone adhesive all around the top adjustment screw & test with a hand pump just out of curiosity. But maybe its normally built to lose pressure somewhere else on shut down, who knows, although that would seem odd where its going. Anyway to stinkin hot here in Southern Cal to do anything with it at this point. 90 in CA always feels like 115 not sure why. Going to get a spark plug wire tester and at least make sure my wire is ok tomorrow giving the neighbors a rest today.

Coming to the conclusion I'll probably just need to take it in as I think I've tried most everything within my capabilities with you guys helping. Put in my plug wire tester today and that once cylinder is getting spark fine. I did put the palm of my hand on each of the individual stacks too on idle and some sucked my hand down pretty solid and some seems like little to nothing. Of course I'm no engine guy but I would assume they should all suck in somewhat equally. Took the engine to a steady 2,000 after warm up and then a bit of backfire as usual. As you guys are thinking I hope maybe it just needs a tune. So, anyone have experience with fuel injection/engine guys in the Southern CA area (such as Huntington Beach, Newport, Irvine area)? I found these guys on the web as one potential source:

Well still fartin around with this. I'm finding many engine/tune shops in the Orange County CA area I talked to won't touch the car. But in talking with one dyno tune guy he said he could tune it after he downloaded the program for the Speed-Pro ECU. But he said all that does is alter the fuel/air ratio going to all the cylinders (not individually). I told him that in putting my hand over the stacks on idle that some sucked harder than others, so he feels I should have the individual throttle bodies synched & adjusted first using a syncrometer tool as shown in the photo before doing a Speed-Pro tune. So I went back to looking at the car myself trying to figure how to use such as meter and where any adjustments are for the butterflies. But in looking around I removed two fuel injection stacks just to see what the butterflies look like and just looking at a couple they seem rather dirty as shown. Not sure if this is my rough running issue or not with maybe all of them being a bit dirty. Kind of hard to believe such little dirt would cause rough running, but who knows. I'm not touching it just yet, as I have read some sources say certain fuel injection systems you should not push on the butterflies to clean the butterflies and walls.IMG_E5138IMG_E5147IMG_E5150IMG_E5155


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I cleaned the top surfaces pretty good with a microfiber and brake fluid, but now need to open the throttle and get inside a bit. I would think the edge of the butterfly valves need to be cleaned as most important, but in opening the throttle 1/2 of the valve will flip downward making it harder to clean. Anyone cleaned these before & share techniques? Even a small toothbrush would be hard to get the flipped down portion of the valve when I open the throttle .IMG_E5330


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I was able to open up the throttle to clean the walls under the valves, but in doing so I saw that while pushing the throttle all the throttle body valves on the right side of the engine were not opening as far as the left side of the engine. Makes me wonder if this may be the cause of the rough running issue or not. I'm no engine guy but I would think the right side should be opening pretty much the same as the left. In the photos below show two throttle bodies (#1 is the left rear side and #5 is the right rear).



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Hey thanks for the drill bit gauge idea. The company said I need to get both sides set at .002 inch feeler gauge with the valves at rest. Says I need to disconnect the cross link (#3) in the photo then adjust the valves and reset the link to neutral. All left side is already perfect at .002, but of course all the right side is too tight at rest. Plan is to get this bitch adjusted today, getting tired of being in the engine bay with numb legs. Usually I'm just in there 8 hours polishing, but this is something else. I guess one benefit is I'm learning something as I go. Not sure if this is my problem issue, but at least the valves should be adjusted correctly if I don't screw something up worse. IMG_E5632


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Be careful when adjusting that cross-link, Jan. One friend with an 8-stack EFI system would NOT hold a stable idle. It ran perfect when cold but different when hot. After much screwing around, it was discovered that aluminum heads and intakes expand when hot and his hot engine was pulling on the cross link enough to change the idle from 700 to 1400 rpms. I think the fix was simply to readjust when hot and accept however it was when cold.

Hot damn you're pretty observant. I have had my head above that engine for a couple days looking at how all the parts work and trying different adjustments. But definitely something is off with the mechanisms that are operated by the throttle. I also pondered weather that cross link got bent or was purposely bent initially so that it enables it to pass under the fuel rails without hitting them because it is pretty tight. So I tried turning it sideways and the left side still opens fully and hits the stop long before the right side opens fully. I'm no mechanical engineer so I'm not sure if turning it sideways would make any difference in the "rate" that it opens the left side, but I tried it anyway and no difference. The right side does work and open fully as shown in the second photo but you have to disconnect the cross link. I asked the manufacturer maybe there are different sizes of levers as shown in the third photo, maybe the black lever should be shorter or longer to slow the rate of the left engine side opening so fast.



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Manufacturer says the linkage is not correct for the left side valves to open quicker and fuller than the right side, but I'm not sure if it came that way years ago from the manufacturer or if someone modified the linkage arm when building the engine. He did say the cross linkage is correct to be slightly bent so it travels under the rails when pressing the throttle. But anyway I have to take things apart and send him the valves & linkage so he can update everything so I need to stick my head in there and see how to disconnect things. But the funny thing is that I adjusted all the valves to his specs at rest (.002 inch) and figured to start the car and see how things run on idle with valves still resting and the engine raced to about 2,500 RPM and backfired, wife crapping the pants in the livingroom. I assume maybe that was due to the Speed-Pro ECU still programed back in the day with dirty valves and now with clean valves and the .002 correct adjustment now things don't match up with the ECU. That is unless something else is still wrong. Finally found my compression gauge in the attic, so I'm going to get to that first. So glad I'm retired to mess with it on and off, but I really would like to drive!

Last edited by does200

Thanks, I offered that up to send the whole unit back but he just wants the valves and linkages. If I'm thinking correctly, if the throttle arm on the right that pushes the cross link to the valves on the left side of the engine was shorter, that should allow the left side valves to open slower (and hopefully match the right side). As far as the engine revving too high on start up & idle after I adjusted to .002 inch, I may close the gap on the valves a little more and see what happens. I am assuming high rev idle could be from the valves still too open, because that wasn't my problem before cleaning & adjusting things (In fact the idle was like 100 RPM).  Im just kind of surprised the engine ran so well all these years with the right side valves not opening as much as the left side.

Ugh, went to check compression by hooking up a remote starter to the starter so that I could turn the car over without the fuel pump going (such as would be the case turning the key on). However that did not work I am thinking because the car has an alarm and maybe that would prevent the car from starting that way unless the key was in the on position. So I am wondering how to disable the fuel pump. Shouldn't there be a fuel pump fuse? I looked in the Pantera manual fuse panel but don't see any fuel pump fuse. I am learning the more these cars are modified, the more difficult they become to work on.

Hi Jan.

The original Pantera’s had a mechanical fuel pump, therefore no fuel pump fuse in the fuse box.

Yours may have a in-line fuse, but you’d have to trace the wires from the fuel pump to wherever it’s powered from.

There may also be Bullet or spade connectors close to the fuel pump. Fuel pumps typically only come with very short leads.

Good luck





Thanks guys, I believe this is the fuel pump. I put my jack away already, so the red wire is easier to get at than the black. Maybe I could just disconnect the red wire & put some electrical tape on the connection or do both wires need to be disconnected to disable the pump? I couldn't find any fuse or other disconnect near by.



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Encountered another thing, looks like there are two solenoids on this car, one on the starter and one shown here. Not sure which two leads to connect with my remote starter so I can crank the engine to do compression check. I was connected to the solenoid on the starter itself so maybe that's why it would not start. Look forward to sometime in 2021 to get this back on the road.



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Connected my remote starter to post 1 and 4 shown in the diagram above and pushed the remote starter button to do compression test but the car still would not turn over. Not sure how else to connect it so I can use my remote starter. I kind of wanted to watch the compression gauge as I turned it over 5 revs, but no luck. So I thought well I will just use the key and turn it over 5 revs then go look at the compression gauge since I already disconnected the fuel pump. But then when I turned the key to the on position I still heard this loud rumble as noted in the video below. I always thought that noise was the fuel pump noise so I was surprised to hear it when I turned the key on. Now I wonder if the fuel pump is really disengaged or if that noise is something else. I would hate to turn the car over with fuel present in doing the compression test.


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Yeah maybe the booster, wife said the noise was coming from the front. So I turned it over with the key for 5 or so strokes and the best I got was 90 on the gauge (not good, I understand 120 & above is about norm). Retested a couple times and still 90. That was on the questionable cylinder that had the low header temp reading. So I'm going to put new plugs in anyway all around and check each cylinder while I'm at it.

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