EFI Conversion won't run cold

[83CapriEFI]

I finally completed the conversion of my '83 to a 1990 EFI set up. The car starts, barely, and runs very rough (engine misses, smells and sounds lean) and won't hold idle without my help. As it warms, it slowly gets better, still missing but holds a rough idle, until about 15-30 minutes later when it is hot and suddenly everything smoothes out and sounds good revving up over 3000 rpm. Here are some notes I took on the computer codes and conditions (with the Innova Ford Code Reader):

After warming up, but not to where it got smooth. Engine off test had code 67 (NPS?-not sure what this is) and continuous memory codes 41 and 91 (O2 sensor out of range lean).

After warming up, and running smooth. Engine off test had no continuous memory codes (but same code 67).

I could not get the code reader to do an Engine on test - I hear the engine rev then it just displays the three zeros - maybe because I can't get a pass code (11) on the engine off test first?

Idle: 800 rpm
Timing: 10 degrees
Vacuum: 17 inches
Fuel pressure: 23 psi on my home made gauge set up - sounds too low? Suspecting the regulator, I tried pinching the return line to the gas tank and that didn't change anything. The fuel pump is pretty noisy but if it can deliver fuel at over 3000 rpm why can't I get more fuel at cold idle?

So far I have had the smog equipment manifold vacuum line disconnected and capped the vacuum tree. I think I am missing one smog component located inside the right fender. According to a vacuum diagram I found it is called something like "VREB??" - couldn't read the last letters. What is this? Would this help it start cold?

[Wildman_302]

not sure why it does that unless your regulator is bad. I am running the 90 efi also , only problem i have (which is not a problem) when it starts it goes to 2500 then brings itself back to idle which is about 1000 rpm with my e-cam. ok there is 2 controls on the fender on the passenger side, do you have them hooked up, ant there is 2 vaccuum canisters inside the fenderwell. Also do you have your purge canister hooked up ?

[83CapriEFI]

The EGR and Air Dump/Divert controls are hooked up on the strut tower but I disconnected and plugged their vacuum source at the intake manifold to make sure it wasn't vacuum leaks causing the rough warm up. The purge canister is also hooked up. I do not have any vacuum canisters inside the fenderwall. I saw these in the repair manual diagrams but thought these might be for A/C (which I don't have). Is one of them the VREB?? Is there supposed to be a manifold vacuum sensor here? I know I have the Barometric air pressure sensor installed on the firewall.

[Wildman_302]

ok i am not seeing a VREB in my ford fuel injection and electronic engine control book. this is the book i used to do my conversion. let me locate a repair manual. one more thing are you sure the IAC is working properly?. take it off and clean it real good with carb cleaner and check to see if you have lots of build up on your throttle body. also make sure your mass air electronics are clean also

[FoxChassis]

"VREF" is reference voltage (+5.0v).

Never heard of VREB.

[83CapriEFI]

The "VREB??" is what I read off the upper left corner of a dirty emmissions label diagram (on top of the coil and starter relay) on a friends 1990 Mustang - I may have misread the letters. Whatever this is, it is located inside the right fender wall and is fed by a black plastic vacuum line that is tied to manifold vacuum after the vacuum check valve on the red line.

[FoxChassis]

Maybe it's "VRES", or vacuum reservoir.

[Mustang5L5]

Fuel pressure: 23 psi on my home made gauge set up - sounds too low? Suspecting the regulator, I tried pinching the return line to the gas tank and that didn't change anything. The fuel pump is pretty noisy but if it can deliver fuel at over 3000 rpm why can't I get more fuel at cold idle?


That's way too low.

You did change out the fuel pump in the fuel tank to an EFI model right? It's a lot higher flow considering stock fuel pressure for EFI is 39psi with the vacuum line off the regulator and can spike to 45psi when the engine is under load.

The stock EFI fuel setup is a return style setup. What that is is TWO fuel lines coming from the tank. The pump must push fuel out at a certain pressure. The fuel regulator is located after the injectors before the return line. It modulates the pressure ahead of the regulator to maintain 39psi and lets the excess fuel flow back to the tank.

Are you running a Speed Density setup, or a Mass air setup.

[Mustang5L5]

Is there supposed to be a manifold vacuum sensor here? I know I have the Barometric air pressure sensor installed on the firewall.


They are the same sensor technically.

If you are using a speed density computer and harness setup, the MAP sensor has a vacuum line connecting the port straight to manifold vacuum.

If you are using a Mass air computer, meter and harness, the port on the sensor is left open and it's now a BAP sensor.


I would look elsewhere other than focusing on the VREB thingy. I know what you are talking about and i have removed it on EFI cars without much drivability probs.

I beleive your concerns are fuel related considering you only have 23psi and code 41 and 91 are left and right bank lean codes. WHat's happening is that on cold startup the car runs ooff the computer and ignores all the sensors and operates on preset fuel and timing curves. You are operating on HALF the fuel pressure you need, so right there you are lean. Now when the car warms up, the sensors come into play. Right off the bat your O2's are gonna sense the lean code and try to fix it. They will increase your injector duty cycle in an attempt to richen up the mixture. That's why you might be able to get it barely running when warmed up. But this is not how it works. You need fuel

Code 67 by the way is Neutral Drive Swith open.

If you can give me a complete list of the setup you are running and all the parts you have i might have a better understanding as to what is wrong

[83gt5.0]

You guys are gonna be a HUGE help to me too. I am about to crank my EFI up for the first time here in a few weeks. I know it won't just fire up and run smooth. I'm never that lucky.

I ended up using an Aeromotive inline pump instead of an in-tank pump. Do you think the stock press. regulator will handle that pump OK until i can get the adj regulator?

[FoxChassis]

The factory EFI fuel pressure regulator will handle an Aeromotive pump just fine so long as the diapragm is in good condition.

[83CapriEFI]

Thanks everyone for the good advice. I think you are right that the fuel pump is suspect; and like I mentioned, I clamped the return line to the gas tank with some vice grips and that didn't help - so the regulator is not the problem yet.

FYI - My exact set up is a 1990 Mass Air engine that I purchased from a local Ford Recycler, complete with intake, sensors, injectors, computer, factory wire harness, etc. attached. I also purchased from them a complete stock dual exhaust set up with O2 sensors, 1990 fuel lines, a stock 1990 fuel tank with internal pump, and an inertia switch. All I did was swap engines, change the exhaust, transmission crossmember, fuel tank, and fuel lines. I wired up the inertia switch, removed the Duraspark module, alternator regulator and rewired for the 1990 alternator (built-in regulator), 1983 starter relay, 1983 coil, and splices for the temperature and oil pressure senders. I also had to relocate the battery to the left side and get a different coolant overflow and wiper fluid set up.

I have the same funky fuel gauge problem and if I end up changing the fuel pump to get more pressure I'll see if I can modify the sending unit (swap wires and add a small resistor?).

[Mustang5L5]

How sure are you that you are only seeing 23psi of fuel pressure?

If you are 100% sure then that is your problem. I only have a 190lph and i can crank my reg up to 60psi or so if i want and maintain it (not that i would) so your pump should be able to easily handle the stock 39psi.

Do you have a blockage? Pump hooked up correctly? Any way you could pick up a stock fuel regulator just to be sure? Have you changed the fuel filter lately?

[83gt5.0]

In my EFI reasearch, I found out you must use an EFI starter solenoid. It has some kind of special protection for the EEC. I would do that ASAP before a $15 solenoid fries a $100 EEC.

[Mustang5L5]

I don't think it's the actually solenoid. If you look at the starter solenoid on my '85 and my '88 they are the same think. It's just the wiring connected to the POS side of the solenoid has an assload of fuseable links and circuit breakers tied into it on the EFI car.

[83CapriEFI]

Problem fixed! It was the fuel pump. I replaced it with a 155 LPH pump from Ron Morris and replaced the sender with an 86 unit from the junkyard. Car started up beautifully and fuel pressure was up to 33-43 psi - and the fuel gauge works now - sweet. This site rules! Thanks for everyones help.

[83gt5.0]

CONGRATS!

Hey 83CapriEFI, do you mind if I bombard you with the EFI questions here in a month or so?

[Zap's 85 GT]

The selonoid issue isnt a big deal. It is just some of the older ones arent diode surpressed. That is just so it doesnt arch as bad across the terminals when you crank it over and the computer sees less of a voltage spike. If there is a replacement selonoid on your pre 84 car chances are that it has a diode surpressed unit. They started incoperating that feature into them in the mid 80's and now they all have them.

[83CapriEFI]

No problem 83gt5.0 - Good luck!