Bucks and dies when boost is called for

Gerry Rider

Registered User
SC has started bucking and starting to die whenever I hit the throttle enough to call for boost. Back off the throttle and it runs fine again. It's also a bit slow to start now. Just finished installing a new big Walbro fuel pump and new pump relay, also a new Screamin Demon coil. Have never had this happen before. Any ideas where to start looking for a problem. As long as I drive it like an old lady it's fine, but no fun having it that way however.
Gerry
 
Put the stock coil pack back on and try it. Some folks have had problems with the demon coil.

Fraser
 
Bucks and dies

No start this morning until I jumped th FP terminal on the VIP connector to battery ground, then rather reluctantly started and ran, but would die if jumper was disconnected. Also still would die if boost called for. Changed to stock coil pack no effect. Pulled KOEO codes and got an 87 FP primary circuit fault, also 95 & 96 FP secondary circuit fault & FP relay open. Relay was new yesterday from Ford. Any other thoughts, I'm too old for this kind of frustration. I'm beginning to question the EEC which has a Dave Dalke chip installed when I put in the 42# injectors.
Gerry
 
There's another thread about having to jump the fuel pump relay at the EEC test plug to get it to start up and run. I believe the thought was that the crank position sensor may have failed or the balancer broke.
 
Bucks

Mike, you might well be right. I read that thread. Mechanic at the Ford dealer suggested checking for a bad ground, probably at the tank. More checking I guess.
 
bucks and dies

Checked the ground at the tank and seems fine. So started disassembling to get at the crank sensor. The harmonic balancer looks fine, thank God. I ordered the sensor from NAPA ($129 in their online catalogue). For info, their item number is ECHCSS407. Will have the sensor on Tuesday. If this solves the problem SCCOA will have come through again when the manuals and the Ford info failed again.
Thanks to all
Gerry
 
bucks and dies when boost called for

Ready to remove the old crank sensor, but so far have failed to find a wrench that will 1st get at the bolt heads (partially behind the harmonic balancer)and 2nd will break them loose. What size is the bolt head? I thought it was a 6mm, but it appears it might be 5.5mm. Need some advice so I can get the correct wrench to do the job.
Gerry
 
if your balancer is older and or not upgraded it will wobble under the extra load of the blower compressing, i had the same issue not long ago, the crank sensor pick up is fine i bet, check for a wobble..
 
Bucks and dies when boost called for

Have failed to break loose the crank sensor bolts yet, even with a tiny 5.5 mm wrench. I have a 5.5mm nut driver on order now, hopefully that will do the trick. For curiosity's sake I ran the test again to see if the upshift light was on while the engine was cranking. It was not; indicating that the cranksensor was OK and that the harmonic balancer was running true enough that it was not rubbing the sensor. Thus a good signal was being sent to the EEC to turn on the fuel pump. Is this really a reliable test of the functionality of the crank sensor and the balancer? If it is then I have some other mysterious problem.
Gerry
 
Not 100% but if the upshift light is going out you are getting a good signal. There is a chance the balancer could have "spun" a bit and thrown timing way off... but still be centric enough to look like its ok.

It wouldn't hurt to check your fuel pressure as well, and since you replaced the fuel pump it would be a good idea to replace the fuel filter as well.
 
Bucks

The light is off while cranking. I thought the balancer was "keyed" to the shaft which would make it difficult to spin different than the shaft. Visually the front interface between the balancer and the shaft looks like it hasn't been disturbed since initial assembly. I'll put the pulleys and belts back on tomorrow and see if it will start and run. If so I can do some more checking like balancer wobble only when boost is called for. I don't have a fuel pressure gauge, but that could be an issue particularly when AFR drops from 14.7 down to 11.5 or so under boost. I'll look into getting a pressure gauge.
Thanks for continuing to check this thread, I need all the help and advice I can get. Oh, I already had replaced the fuel filter.
Gerry
 
The extended hub section of the balancer that goes into the timing cover seperates from the front main hub. Its a common failure point and it can seperate before the key so then your depending on the interference fit to spin the balancer.

Fraser
 
Bucks and dies

Finished reassembling everything this morning and tried to start it, with the following result and observation;

1. No fuel pump run, no start unless the FP terminal of the VIP
connector shorted to the battery ground
2. Engine idles smoothly, but quits seconds after the above connection is
unhooked.
3. "upshift light" goes out when engine is cranking, assumed that
Crank Sensor and Vibration Damper are OK i.e. good signal of
engine rotation going to EEC
4. No observable significant "wobble" at the vibration damper
at either idle or as RPM is increased.
5. Fuel goes very lean (AFR>20:1 per LC-1) when accelerator is
hit to WOT, engine bogs down and dies very quickly. No observable
positive boost seen.

Fuel pressure gauge ordered from BBK to observe pressure, will take a few days to get it. I am now believing that the fuel pump problem is indeed a less than desirable ground. Will rewire a new ground path next. The WOT leanness and quitting with no boost remains a mystery. I don't know what to do about that except check fuel pressure as soon as I can.
Gerry
 
5. Fuel goes very lean (AFR>20:1 per LC-1) when accelerator is
hit to WOT, engine bogs down and dies very quickly. No observable
positive boost seen.

Fuel pressure gauge ordered from BBK to observe pressure, will take a few days to get it. I am now believing that the fuel pump problem is indeed a less than desirable ground. Will rewire a new ground path next. The WOT leanness and quitting with no boost remains a mystery. I don't know what to do about that except check fuel pressure as soon as I can.
Gerry

If you are running the car in Park, it's hard to make any boost. If you ran it on the street, then never mind.

Did you check the vacuum to the FPR? Or check to see if it's leaking?
 
didnt see anyone say anything about a DIS mine was some what drive able till hitting into boost when the DIS crapped out
 
Bucks and dies

It's a 5 Spd that I'm running in neutral. My no boost statement is wrong. When I punch the throttle to WOT, the boost gauge zips right up over 10psi, but the AFR climbs to very lean, >20 and the engine dies. My speculation is that fuel pressure is low and for sure is not maintained for even a short time,after the engine shuts off. The fuel drains back to the tank quite quickly after the FP shuts off, making it hard and slow to start after sitting for a while. I'm not sure, but this may also create the lean situation when the throttle is punched quickly to WOT. I'll have fuel pressure gauge in a few days to check it, but there is obviously a pressure leak some place. Maybe the regulator is the problem source as you suggested.
 
Fuel system woes contiue

Changes and results to date:
1. Found the supply hose loose at the new fuel pump (probably pulled loose when installing the long unit into the tank). Fixed that, which solved the lean problem under boost.
2. Engine only starts and runs when pump is jumped to ground at the battery. Quits if this ground is disconnected. Checked the ground wires and connections. All seem good. There is continuity and low resistance between the fuel tank connector ground and the chassis implying that there is a good ground in the entire of that line. Balancer and crank sensor seem OK.
3. Installed a pressure gauge in place of the Shrader valve which reads a steady 34 psi whenever the fuel pump is running. Pressure drops to zero as soon as pump shut off and fuel starts draining back into the tank.

Conclusion is that there are 2 problems.
a. Bad pressure regulator, not holding pressure and allowing fuel
to quickly drain back.
b. Electrical fault someplace. Something is not triggering the
fuel pump to run when the engine starts. Relay is new, so
I'm suspecting that the EEC may not be closing the Fuel pump
circuit.
If true, both are very discouraging. One is expensive and the other is a buster to get at and change. Anyone have any other thoughts?
Gerry
 
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