MFI Running very lean on one side??? Help?

[mikey74]

First off, airflow is the same on left and right bank. THis is a 2.4E Motor that has been sitting a while. Injection pump was rebuild prior to motor sitting. Motor runs like POOP and temps on left bank get real high quick. What weird is when I pull those lean injectors when I get them out they pop and shoot fuel out the inlet? IS there a check valve inside injector? I can't imagine that three on one side are bad so I'm thinking could it be the pump? I have a bosch injector tester w/o a pressure gauge. They all seem to spray OK. I think that when I first went to start the motor I cracked the other banks injection lines to bleed them so the motor would start. Help I'm stumped?

[Grady Clay]

Good that there is proper air flow on each bank.

Whenever there is something that is bank specific (1-2-3 is different from 4-5-6) ALWAYS check the cam timing on BOTH sides. A little assumption here can lead you down the wrong path big time.

The second step is to do a complete cylinder leak test. Cranking compression is nice also.

Knowing for sure these test results are in spec allows you to look at the MFI with some confidence.

The MFI pump is obviously suspect as it has been recently tinkered with internally but lets not jump there yet. The pump has two rows of pump pistons and check valves. The left row is for the 1-2-3 cylinders and the (slightly offset) right row is for the 4-5-6 cylinders. The piston-cylinder-metering system and check valves are all relatively independent. The cam that operates them is common to both rows – nothing is separate for the two banks.

I would look at the throttle linkage next. Check to see that both links from the cross-shaft to the throttle bodies are in place. You probably checked the air flow among the stacks at idle. Check the flow at high free-rev part throttle – say, 3-4000 rpm using the hand throttle. When you go to full throttle at the accelerator pedal, are both banks (check all six throttles) at or near wide open?

Please report your findings.

Best,
Grady

[mikey74]

I've pretty much done that. Overlap is about 3.2mm on both sides which I think are close or pretty close for an E. Compression is OK. ROds are all adjusted correct. Air flow is same both sides idle and off idle? There is a noticeable squeak consistant w/ engine rpm on the lean side though. Big intake leak? I appreciate your help.
Mike

[Grady Clay]

Mike,

A couple of simple tests:

Swap all the nozzles L-to-R; 1-to-4 and 4-to-1, etc.

You said that all six nozzles have identical patterns. Do they seal when not spraying (no drips) but have some pressure? Do they ‘chirp’ when you suddenly operate the nozzle tester?

Do you have the Factory air filter or two (K&N) element filters? If 2-element, try swapping them L-to-R.

Check for vacuum leak at the head-to-throttle body interface. Really good nozzles give a noticeable ‘chirp’ at idle. Usually old rocker arm shafts, loose pistons and worn throttle shafts ‘clatter’ so much they mask the nozzle ‘chirp’. It sounds like you gave a good ‘tight’ engine.

The 2.4E cam timing spec is 2.70 to 3.10 mm at TDC Overlap and 0.10 mm valve clearance. With identical 3.2 mm measurements, this shouldn’t be your L-to-R issue.

What do the sparkplugs look like?

Tell me more about the poor running. Does the one bank run lean at idle or just under power? If too lean at idle, I would expect lots of ‘popping’ back through the intakes.

Another possibility is the engine ‘ate a rag’ where there are chards of rag on one bank. The same possibility is the case for a mouse nest on top of the cylinders and heads on one side.

Best,
Grady

[mikey74]

Welp, seems to be fixed although I'm not sure which was problem. I swapped left benk injectors with some from another running mfi setup. I also was able to easily turn TB to head nut on #1 almost one turn. The other two not so much but still seemed loose. So vacuum leak? Although it sure was weird when I pulled the injectors at first and once I pulled them out they sorta popped and fuel spayed out inlet. Weird. I appreciate your help. I've dealt with a lot of MFI cars but this was strange. Unfortunately, you might see the car up for sale soon. It's a just about concours ivory 72E coupe. I've got a new business and need some $ so it might have to go.
Thanks again for the obviously well experienced advice,
Mike

[Grady Clay]

Mike,

Lets swap the nozzles back into the 1-2-3 side, one-at-a-time until the problem reappears. I can’t imagine an issue starting simultaneously with all three nozzles on the same side of the engine. It is far better to actually find the problem than have it simply ‘go away’ only to reappear sometime later. That usually happens at the most inconvenient time. Murphy sees to that.

At some point it might be desirable to install new gaskets around the throttle bodies. A big leak can actually suck in part of the gasket and the engine then ‘digests’ it.

There is a check valve in the fitting at the top of the MFI pump. That valve allows easy flow from the pump to the nozzle. The nozzle is actually a ‘check valve’ in both directions. It only flows in the forward direction when the pressure gets to the (~134 psi) opening pressure. The point of this is to maintain residual pressure to prevent boiling the gas in the nozzle and pipe by keeping the fuel at a high pressure, hence a higher boiling point. If the gas does boil, the vapor condenses on cooling and the resulting vacuum draws in some more fuel from the pump. Vapor lock prevention.

The shortcoming of the design is the MFI pump is half gasoline and half hot engine oil. This allows the fuel to boil in the top of the pump. To be really effective the electric pump should continue to circulate cool fuel during the cool-off period.

Trivia of the day.

Best,
Grady

PS; You have PM.