Furry companion being me. So I bought a car, and it has this in it.
And these things.
and this thing
one of these
umm, this also.
a dial for measuring the pressure of it's fuel.
And lastly, this.
So to surmise. I have never had one of these FoMoCo things, and never had an engine with all this stuff on it. All would be great if... it actually ran right. When I went to test drive it it would fall on it;s face at 3000rpm's. I said "what the hell, that can't be that hard to fix" and bought it anyways. It has an Edelbrock Victor EFI 5.8 manifold, EdelBrock aluminum heads with unknown valve train components, unknown cam, and all this MSD stuff you see. Well I go to pick it up the next day and it won't even idle without me giving it gas. I got it home and threw the battery on the charger to make sure it had a good charge, and tried again, and again, it won't stay running without throttle input from me.
I'm gonna need some help on this one I think. If I where a Ford guru, where would I start? Unplug the MAF? I checked my grounds, they looked good. I probably need to get a timing light for this one.
So help me Obiwan Ken-GRM, you're my only hope!
What kind of fuel pressure are you getting at idle?
Filters new? Fuel pump on its way out?
The good news is, you can change a lot of that stuff back to reliable, factory parts and not lose any power.
Get the TFI module checked at one of the big box stores. Get a timing light on the thing and see what's going on there. Change the fuel filter.
What TFI module? The only Ford part left in the ignition system is the key 
IMO engine mounted fuel pressure gauges are fire hazards. Yeah, I know lots of people use them. I've seen two leak. Two is two too many for me to trust them.
That MAF is one of those funky aftermarket ones that has its airflow/voltage curve tweaked so your computer will work with larger injectors. Except, that never really worked all that well and was a Band-Aid kludge from the dark days before easily reflashable computers. If it were mine, I'd yank the MAF and any other fuel-related hokey aftermarket stuff and go to a nice standalone.
After checking the basics - is timing okay, are there any vacuum leaks, etc.
Start with the basics... Check for vacuum leaks, loose wires ect...
What you're describing sounds like a low-voltage issue somewhere in the ignition.
Check your grounds, make sure you've got a nice fat wire feeding +12V to the ignition box and the coil.
If all that is ok and you've got good fuel pressure, I'd remove all the ignition garbage and put new OEM components in to eliminate the msd as a source of the problem.
You can always put the Edelspark stuff back on later or sell it to someone who doesn't understand electricity.
When my old carbureted chevy truck pulled the "flat on its face after 3k" stunt it was because I bought a new edelbrock cam, performer aluminum heads, manifold, and carb, and it made the vac advance in my stock distributor all catty-wompus. An adjustable vac advance canister from accel was the fix for that one. But I'm pretty sure your advance would be computer controlled... Not sure how you would change that.
The flip side of the "timing" issue (to see if we're dealing with the same demon) was I could time it to 28deg advance 3000rpm (iirc) by adjusting the idle waaaaay high and using the delay feature on the HF timing light I borrowed. When that was done, it had no guts below 2600rpms but pulled like a champ through 3000rpm on up to about 4500 rpm where it started to lose power again.
When my brother's 240sx engine (transplanted into a Datsun pickup) pulled the "wont idle, falls on its face at about 4.5k rpms" stunt it was a vacuum leak at one of the hose clamps on the intake track. I'd double check that all the hose clamps are on tight and that there are no vac leaks. Anything on your intake track after your MAF sensor is worth a double-check.
My Alfa (the one time I drove it) had a bad idle, slow to accelerate, then felt like it "came up on its cam", only to fall flat on its face again. Turns out the previous owner timed to the wrong mark on the crank when he installed the timing belt. Not sure if that's a possibility with your engine.
Good luck man!
The only issue I've ever seen with MSD is due to people ignoring the instructions and splicing the large red wire into something.
The large red wire really does need a direct battery connection. It doesn't tolerate voltage drop. The way the ignition system works, you need to nearly instantly charge a fairly large capacitor, which will have an instantaneous current draw of up to 30 amps.
Is that the Mustang I think it is?
Used to be rather dirty?
Thanks for the suggestions guys. I'm going to try and get it unloaded from the trailer and start messing with it today. I'll check the electrical connections to the box and see whats going on there. A trip to Harbor Freight for a timing light looks to be in order also.
@The_Jed; Not sure what Mustang you're referring to, this was one I found on CL and wasn't particularly dirty..
That fuel pressure seems low. The 5.0s are at ~40psi IIRC.
I know on my fox, when the pump was failing it would fall on it's face, as you described.
It looks like that's an SN95 car. The Ecu on those has a few more nannies that are less sympathetic when you mod them. Any idea if it has been tuned?
Cooper_Tired wrote:
That fuel pressure seems low. The 5.0s are at ~40psi IIRC.
I know on my fox, when the pump was failing it would fall on it's face, as you described.
It looks like that's an SN95 car. The Ecu on those has a few more nannies that are less sympathetic when you mod them. Any idea if it has been tuned?
Yeah it's a '96 SN95, allegedly the car ran great when the guy who bought it before me got it. That pressure reading was after I shut the car off, I couldn't keep it running long enough to check the pressure while it was. I also have no clue what ECU tuning was or wasn't done to it. So I might just scrap all the electronics and go individual coil with a crank and cam sensor. But I would like to get ti running right with what is on it if possible.
A '96 would have had a 4.6 in it. Ford didn't certify the 5.0 for cars past 1995.
It also should have Hydroboost.
I wonder just what it is you have, now. V6 or V8, it would have had the electronics swapped too.
t25torx wrote:
Thanks for the suggestions guys. I'm going to try and get it unloaded from the trailer and start messing with it today. I'll check the electrical connections to the box and see whats going on there. A trip to Harbor Freight for a timing light looks to be in order also.
@The_Jed; Not sure what Mustang you're referring to, this was one I found on CL and wasn't particularly dirty..
Dangit, I missed the strut mounts. Dead giveaway that it's an SN95, not a Fox like I had assumed.
I thought it was Nonack's old Mudstang that was bought by TDRRally. I thought maybe he had sold it to you.
Okay so I think I found the fault with it not wanting to idle. I got to thinking about the BMW I fixed a while back and how it also wouldn't idle without assistance from me, that one was due to unmetered are getting in behind the MAF due to a tear in the intake boot. So that's where I began. And low and behold the intake boot connected to the throttlebody was crooked and a gap had opened up on the bottom side. So I took all the intake parts out and refit them together taking care to tighten all the clamps good, I also found the IAT sensor was fit into the hole using masking tape and RTV sealant to seal it to the intake. I removed all that crap and found a nice rubber grommet that would fit in nice and tight.
I also took a look at the MSD box to see how that was wired up, and turns out it wasn't. The only things connected to it where the ground and power wires, the TFI harness wasn't even connected to anything. So I just removed that completely to rule it out as a suspect. Now was the moment of truth. Turned the key and it started, but wouldn't idle right off. So I sat there giving it gas and then suddenly the engine note changed and she was idling by herself. Huh.. so I took her for a spin around the block and still falls flat on it's face at 3k rpms. Well I guess that's an improvement. I'll keep working on it this week.
For what it's worth it's actually a '95 GT that the previous owner swapped this stroker 351w into. The fuel pressure at idle was around 25 according to the gauge on the fuel rail. I'll try putting the MSD in correctly tomorrow and see if that helps anything.
Yeah, a leak after the MAF will make it idle like crap.
Falling flat on its face above 3000 sounds more like a fuel problem to me, especially since the previous owner installed a fuel pressure gauge (trying to debug this very problem?). I second the idea of checking the filter and the pump.
After that, I'd look at the electronics. Do you know what computer is in it? Is the stock 95 one (I think that's an EEC4?), or did it get swapped along with the motor? What size injectors does it have? Can you get any specs on the MAF?
I believe there are tools out there to let you tune the EEC4 yourself, it might be worth looking into that. A 351 with a big pile of hot-rod parts seems unlikely to run well on a factory computer, and a proper tunable standalone system will make a huge difference.
I've seen a couple cases where people screwed in those fuel gauges too tight blocking the flow of fuel. Might try a plug to replace the gauge & test drive to see if it still falls flat.
replace the pump with a GSS340 walbro unit. do not install the stupid MSD thing. its useless.
enjoy!
-J0N
What's controlling it? A '96 should have an EECV, but tuned for the original engine. A swap like this- did they bring over some other module??
I'm hoping that with those 42lb injectors, that it's running really rich at 3000rpm, which is where the car probably is going from closed loop to open loop- relying much more on the MAF-injector calibration matching properly. The injectors are way more than it really needs- those are good for boosted engines. I'd look at re-doing a lot of that set up.
(note- 29psi at idle is fine- the pressure is relative to manifold vacuum, 39-MAP is what it will be)
Thanks for the information guys, I'll start digging into the electronics tonight when I get home to see what's running this thing. and yeah I was thinking those green tops might be a bit overkill for this thing. Good thing is they sell for a decent amount online so I should be able to do a swap for smaller ones and not be be out anything.
Okay so I took a look at the ECU tonight. It's an EEC4 that looks to be stock. I don't see any markings on it indicating that it might have a chip or any aftermarket tuning capability. So that's would be a good start as to why it runs poorly. I also took a short video of what it's doing in case anyone cares to watch.
https://youtu.be/vVvrmH6_7VY
I drove it around again, and once it hits that cut off if you keep it floored it just keeps dying, and finally about 1000rpms it'll buck and spit and backfire like a shotgun. So awesome stuff. I'll pick up a timing light tomorrow, but I have a feeling the timing isn't getting advanced.
The idle seems a bit high and it sounds like it may be intermittently pulling timing...or something. It seems like the idle dips a bit after the engine gives a "bloop" sound and then it sounds like it's under load for a moment or two.
The cam seems either very mild or O.E. That surprised me a bit. I would assume if the prevous owner went to the trouble of installing aluminum heads and a Victor intake he/she would have stabbed in a hot cam as well. Curious...
I've heard the SN95 EEC is not tolerant of any sort of modification that monkeys with the vacuum signal. Maybe it's throwing a fit over the added displacement?
I concur on the timing light suggestion.
Being a '96, that car should have an EECV, which would be OBDII compliant. So the module was apparenlty changed with the engine swap.
Question for you- how much are you willing to get into this job? These guys have a lot of software tools available to work with- http://www.moates.net/ford-19862004-c-63.html which are similar (not the same) as the tools used to calibrate that.
To get the engine that module is for, you'd have to look up the SN and the flashed software on it. But assuming it's for an earlier 5.0- the quick way to update it is the cylinder info (easy to calculate), the MAF transfer funciton (which I would hope is somewhere up on the interwebs), and the injector data (same thing). Those three things would go a long way getting this engine running well. (really well, actually)
If you are really brave, you could get the tuning software, and really customize the calibraiton to run better.
But at a bare minumum, one needs to look up the MAF sensor, and it's intention. With that, you can compare it to the one that was original with the module, and then check the injector sizes better.
With a MAF system, the cams don't really matter much- air flow is matched with fuel flow.
Anyway, get more data off the module and the MAF and lets figure out where they were going.
One thing about the timing, there's a little short in the harness that will tell the spark to just sit at 10. If it's always at 10deb BTDC, that is missing.
