Something's wrong and I can't figure out what

[deffman32]

Sorry this is my first time using a forum...
I just bought a 1991 Ford Festiva. I got it home, tinkered around, gave it a tank of gas, and was able to drive it around the block just fine. I came back the next day and it just wasn't starting. The few times it started it would slowly taper off and die. I got a fault code of 81 but I have no idea what's wrong! 177,000 miles... Bought it as a project.
Let me know any extra info you need! I welcome any help!

[WmWatt]

You have used the correct forum correctly. Unfortunately the Haynes manual does not show a code 81. It shows codes on the 1990-1995 EFI engines between 01 and 34 inclusive. Also a search on "code 81" (see search box top right of screen) does not return anything on that code. Out of curiosity which method was used to retreive the code?

I just did a Google search of the Internet on "ford festiva code 81" and got some hits. While waiting for replies here you might try looking at some of those.

[WmWatt]

I just did a Google search of the Internet on "ford festiva code 81" and got some hits. While waiting for replies here you might try that.

[deffman32]

I re ran the codes, I was reading them wrong. It's actually 8 and 10 which comes out to problems with the airflow sensor and the intake air temperature sensor.

[WmWatt]

I have the carburetted engine so no personal experience but over the years have read about common problems with the MAF(mass air flow?) sensor on fuel injected engines. You might try a search on the sensors. Hope that works.

[WmWatt]

Back again Don't know how familliar you are with engine controls but where vacuum lines are involved somtimes it's just a hose which has worked loose. All it sometimes takes is pushing the hoses to ensure they are on snug to fix a problem.

I remember with the fuel injected air intake the pivot can get dirty and the vane sticks. People have posted here that cleaning the sensor fixes the starting and stalling problem. Maybe yours too.

[deffman32]

I appreciate the help!
I've already tried cleaning the sensor, it didn't seem to work. I might need to check the hoses though, thanks for the advice!

[deffman32]

The hoses all seem to be attached properly... Could it be the ecu?

[WmWatt]

"slowly taper off and die" sounds like starvation or strangulation. I would be inclined to look at fuel and air supply first as being easier and cheaper than ecu. Usually check for dirty fuel filtre and maybe disconnect the fuel line and see if fuel squirts out, that sort of thing. The screen on the fuel pump inside the tank can get clogged. There are also the fuel injectors. I've read they can become dirty.

Then for air flow there's always the air filtre and those sensors mentioned above. Sensors can usually be checked with a volt/ohm meter. Haynes (pg 16-11) says on 1993 and earlier model the intake air temperature sensor is incorporated into the airflow sensor. (Haynes tells how to check sensors. Info maybe avail online.) It does say the ECU should be providing 5v and if not have it checked. However it's good to inspect wires for bad conections, worn insulation, etc. first.

[deffman32]

I believe it is being starved. When I turn the key with the fuel hose disconnected, it squirts just fine. I believe the next thing to check will be the fuel injectors as they are next in line after the fuel filter, but fuel is going through the filter fine.

[1990new]

Welcome to the forum.

As WmWatt explained:
There are many factors in play in the EFI system. Many sensors send signals to the ECM and the vacuum systems is very much involved.

One of these components is the fuel pressure regulator which is very much dependent on the manifold vacuum (as are other components involved in the smooth operation of the engine).

The outlets of the fuel injectors are exposed to manifold vacuum/pressure which varies depending on throttle movement, but the flow of fuel from the fuel pump is constant (that is constant when the fuel pump is running and for the fuel pump to be running the key must be in the start position or in the on position and the ECM is getting a signal from the VAF that air is flowing), the fuel pressure regulator valve needs a reference to continuously change the amount of fuel bled to maintain constant fuel pressure to the injectors. The spring force in the fuel pressure regulator closes the valve when there is no vacuum in the intake manifold. When you start the engine the difference in the ambient air pressure and the vacuum pressure caused by the piston suction is present in the intake manifold and that vacuum pressure that is carried from it thru the hose to the pressure regulator increases the pull on the regulator valve opening it up. The vacuum is greatest at engine idle and least at wide open throttle. So what the regulator is trying to do is to maintain a constant pressure difference between the inlet and outlet of the injector.

The ECU is very well protected both physical and electrically in these cars and 99% of the time it is not the problem.. but it cannot be ruled out.


Caution: If you search the forum you will run across a number of posts that members have made about the destruction of their Festiva by fire.
Your statement about fuel squirting brings this to mind. A word to the wise.
Always..Always..Always have a fire extinguisher handy anytime you are testing the fuel system.

[deffman32]

I appreciate all the help! A family friend suggested replacing the fuel pump anyway. I just finished and now it works fine! Again, thanks for all the help!

[1990new]

I appreciate all the help! A family friend suggested replacing the fuel pump anyway. I just finished and now it works fine! Again, thanks for all the help!

Happy to hear you got it running.