Engine spins but does not fire

[Larry_S]

A couple years ago the engine in my SVO failed due to detonation and broke part of piston. SVO is an 84 and has a PE with wire mods made in harness. I plan to change harness back for 84 computer but do not want to change too many things at once while trying to get running. I recently installed an 84 engine that has been sitting since some time in 84 I suspect as it only had 4700 miles on it. The car it came from must have been an early fatality. Anyway I haven't checked fuel pressure yet but it seems to be getting fuel as the fitting that enters the fuel pressure regulator was leaking with key forward due to o-ring not sealing so I just replaced that fitting. I don't know a good way to check spark but with the plug out of engine attached to wire while cranking sparking could be seen. With the engine at TDC and the cam pulley mark lined up with timing mark I have the #1 of cap approximately over the rotor. Engine is turning over strong but no attempts of firing.

[Laredo]

Can you borrow / rent a fuel pressure gauge? It only takes a few #'s of pressure to leak, but you'll need more than that to start the car. Or...see if it fires/starts by spraying carb spray or starting fluid in the intake air tube.

[Larry_S]

I installed a fuel pressure gauge and when key is turned on pressure goes to around 10psi. While cranking it works up to 42psi or so. Are these numbers low? Under normal circumstances what should fuel pressure go up to during key on and also while cranking? If the pressure is low does this indicate the fuel pump relay is working but the pump is not providing enough pressure? A couple years ago I removed the external pump and installed a single higher psi pump. 190 comes to mind.

[SVOC]

Don't forget, just cause you have pressure doesn't mean you have volume ;)



http://oldfuelinjection.com/images/tools17.jpg

[MikeFleming]

10 PSIG is not enough pressure to make droplets from the nozzles while 42 is. Pull a plug and see if any fuel is getting into the cylinders.

Do you have a noid light?

Are you certain the distributor is rotating with the engine?

As a side note there are no wiring changes between any of the SVO processors, such TE & PE.

[Larry_S]

While cranking the pressure is around 42psi. However if I just turn the fuel pump off and on with the key while transferring fuel to a water bottle with the relief valve depressed on the fuel pressure checker the water bottle does not fill with fuel very quickly. I do not have a noid light set but if autozone or oreilly etc has one I will pick up tonight. Distributor is rotating. As for process thanks for clarification i think I may have been confused with when I was going to install an LA3 but changed my mind. I'll install the TE when I get a chance.

[Larry_S]

I took a couple videos. The first is my son turning key on /off 3 times and then cranking engine. The second is my son cranking engine while I am holding relief valve on fuel pressure tester. It does not seem like there is much fuel traveling through system into bottle. However I turned key off and on many times thinking it would put enough fuel in system to at least fire off even if it would not sustain but the engine will not and has not fired or attempted to fire once. Also I do not notice a heavy fuel smell such as a flooded condition.
http://mc2.gotdns.com/photo/photo_thumb.php?dir=73766f2f38345f32412f68616e6761725f717565 656e

[MikeFleming]

Sounds like a few issues in the fuel system.

1. It's not holding pressure. 84 models have two fuel pumps, a low-pressure in-tank and a chassis-mounted high pressure one. There is a check valve in the exit of the HP pump and if that fails, the system will not hold pressure. Naturally if you have a bleed hose connected to the schraeder valve to measure flow, as soon as the pump(s) stop, pressure will drop even with a good check valve.

You can jumper the pump(s) to run all the time with the key in run by using the self-test connector and a jumper wire. Jump between the indicated wire and a chassis ground. See here:

http://www.svocop.com/forum/showthread.php?516-Fuel-system-question&p=2921&viewfull=1#post2921

So test the actual fuel flow again with the pump(s) on continuously. Then close off (or disconnect) the bleed hose and see if it holds pressure after pump(s) are off. Should hold to a minimum of 15 PSIG for 20 minutes.

2. When you said you had spark, where was that measured? At a spark plug with the body grounded - after the distributor and rotor? You can also do that with the distributor end of the coil wire. The sparks should look the same brightness and length to the naked eye.

3. Get a can of starting spray (usually 80+%+ either). Remove the charge cooler and spray a TINY amount into the throttle body then try to start it. If it attempts to catch (note it will rattle/ping the whole time - use only in a well ventilated area), then you know ignition, compression, valves, and other stuff are close. And have a fuel delivery problem.

If it DOES NOT fire at all, you have a mechanical (compression, valves, cam timing, ...) or ignition problem.

Troubleshoot what's not working. Remember to test/verify one system at a time. Repair as needed, test again then move on to the nest system.

Lather, rinse, repeat.

We'll be here when you need us.

[Larry_S]

1. A couple years ago I removed the external pump and installed an internal 190. When jumpering test connector pressure builds up to 42 psi and when I removed ground pressure drops to 30 or so and holds for a long time.

2. To measure spark using a tester set to 30 spark was jumping across the two points. This was tested out of the coil and out of the #1 plug. I think 30 means the system is producing 30k volts charge. http://mc2.gotdns.com/photo/convert.php?dir=73766f2f38345f32412f68616e6761725f717565656e&name=737061726b506c75675465737465722e6a7067&type=5&v=0

3. Engine runs with starting fluid.

Something of interest is on my running SVO when I install the pressure gauge and turn on pump via test connector the gauge builds up pressure and that's about it. On my non-running SVO under same conditions I can hear what sounds like a vacuum leak but I wonder if it is the fuel cycling through the system and out the return line. So with the test connector turning the fuel pump on is any of the fuel suppose to return to tank? Is it possible on my non-running SVO when the fuel pump is on all the fuel is returning to the tank and not getting to injectors?

Also the fuel has been in the tank for over a year. I added a couple gallons 93 octane but I have never had to actually remove all the old gas to get a car to start that has been sitting for a while.

[MikeFleming]

Fuel is always returning to the fuel tank - unless the power requirements of the engine are greater than the fuel pump capacity. As long as you have measurable pressure, there is fuel flowing past the regulator into the return line to the tank.


3. Engine runs with starting fluid. Good news indeed. Very good news.

It's *possible* to have some plugging in the fuel rail itself, but very unlikely. If the car sat for any extended time period - say more than a year - then the petrol that used to live inside the injectors has probably turned into muck (a technical term).

Pull the upper intake off (access is much easier) and take out the fuel rail to manifold bolts. Lever the rail back - with injectors still inside it - enough to where all four injector tips are exposed. Unplug three injector electrical connectors and cover the connected injector's tip with a ship towel.

Remember that the fire bottles should be in the exit path - not further into the shop. In case you ever need one.

Then have someone crank for two seconds while you watch the spray pattern from that injector. Switch to next injector - rinse, lather, repeat. I wonder if I have any recent pics of a good pattern? It should be a VERY fine mist in a large cone pattern. If it's just pissing out in a single line, they need to be cleaned or replaced.

[Larry_S]

Thanks for ideas Mike. I will try what you say however for the record I did replace the fuel rail, harness, and injectors with another assembly today. I found the following image on ebay depicting spray pattern: http://mc2.gotdns.com/photo/convert.php?dir=73766f2f38345f32412f68616e6761725f717565656e&name=45355a45413342312e6a7067&type=5&v=0

[Bob Holmes]

Drain the fuel and start fresh.

I'm surprised at how much your engine moves, have you checked the mounts?

When you pull the plugs, what do they look and smell like?

Bob

[Larry_S]

Draining fuel now. As for the mounts I just installed engine and torqued mounts. They seemed ok. I do not have engine shocks installed at the moment. Plugs are new but look a little wet now. I don't have a very good sense of smell. Pics of one of the spark plugs: http://mc2.gotdns.com/photo/photo_thumb.php?dir=73766f2f38345f32412f68616e6761725f717565 656e

[Larry_S]

While draining fuel I timed 2 gallons of fuel into a gas can and it took ~ 2mins 20sec which comes to about 195liters/hour so since I installed 190lph those numbers are adding up yes? So fuel pump seems to be working ok.

[MikeFleming]

^
Correct. Looks like the fuel delivery system is OK.

[Larry_S]

Drained fuel and put fresh 93 octane 2 gallons in. Primed system before I reattached the supply line to regulator. Still not firing. I'll check the injector spray pattern next.

[Larry_S]

Removed upper intake and while cranking engine no fuel is coming out of the injectors. When I look at the voltage with an oscilloscope I can't really capture what is happening as there is a lot of noise on line with only power applied. I tested one injector at a time and none of them are allowing fuel to pass. Are the injectors ground switched to activate? Is there 12V on one side of injector and the other side is switched to ground when ECM calls for fuel? Assuming this is true I applied fuel to rail using test connector and with 12V applied to one side injector I momentarily applied a ground to the other side and no fuel sprayed out. Is this how the injectors should work and therefore is it possible all 8 injectors I have tried are clogged? Before I take to the diesel shop to have flow tested is there something I can soak them in to try to clear out if this is in fact what the problem is?

[Kendal Coker]

I have taken a sharp pointed screwdriver type insturment and poked the end of the injector to get them unstuck. Sometimes it works sometimes it does not.

[MikeFleming]

If you have the stock pintle-type injectors, be very careful to not bend the pintle tips. Maybe soaking the whole injector (tops, body, top inlet) in isopropanol (rubbing alcohol) will help un-gum them.

[Larry_S]

Injectors were cleared up, verified good spray pattern, and car lives again! Thanks guys!!

[MikeFleming]

Party On, Wayne!!