[mobiledj911]

I have a 1989 Ford F-350 7.3l Diesel and am wondering:

1. How many glow plugs have to fail to make the engine?
A. Hard to start
B. Not start

I have:
1. Checked all the glow plugs with a continuity tester and they test OK
2. Checked the glow plug controller (both voltage & timing) and it is OK

Here are some facts/observations:

1. Summers temperatures when trying to start are 70-80 degrees
2. The engine always starts after the block heater is plugged in for a few hours.
3. The engine runs strong once started
4. There are a few glow plugs that are hard to reach and I am wondering if 2-3 being out can cause this issue in summer temps?
5. I do notice that there is some air in the fuel filter (press on value occasionally and fuel does not squirt out, some air (for 2 seconds, then fuel or air, no fuel until it cranks a few times) (Could it be related to fuel delivery?)

I would like to also know if anyone has some ideas about the best tool/way to get to the 3 or so glow plugs that are mid-engine and seem to be blocked by the metal fuel lines? The F-350 is a van with the typical problem of the engine not being out in the open as a truck with a hood would be.

Thank you!

 

[standbypowerguy]

Checked all the glow plugs with a continuity tester and they test OK.

There are a few glow plugs that are hard to reach and I am wondering if 2-3 being out can cause this issue in summer temps?

So I gather you really haven't checked all of the glow plugs...

Yes, two or three bad GPs will cause the controller to time out early, which leads to insufficient heating of the remainder and results in hard cold starting, even in summer. I suspect you've probably got some marginal GPs, which won't show up with a test light. To properly test the GPs, you need an ohmmeter or multimeter. If your meter is not auto-ranging, set it on the OHMS scale (not micro, milli, kilo, or mega) then securely ground one of the probes to the engine block. Touch a clean spot on the block with the free probe, the reading should be zero or very very close to it. If it's not, redo your ground, connections must be clean. Disconnect the plug off the top of the GP under test and touch the free probe to the tip. a good GP will read 2 ohms or less, anything higher is marginal and should be replaced. Replace only with Motorcraft/Beru ZD-9, if you find any that are not marked ZD-9, replace them all. There's also a Wellman dual-coil model that's good too, if memory serves it's P/N 84. Replace GPs as a set so they work together in unison.

As far as reaching them to test, even in a truck the ones under the injection lines require contortions and patience. I use various sets of needle-nose to pull and plug the connectors and a 1/4" drive deep socket with a swivel and various extensions to remove the plugs. If all else fails, you can remove the injection lines, but I've never needed to.

I do notice that there is some air in the fuel filter (press on value occasionally and fuel does not squirt out, some air (for 2 seconds, then fuel or air, no fuel until it cranks a few times) (Could it be related to fuel delivery?)

You bet, or more precisely, drain back. This can cause hard starting, but ususally results in a start followed quickly by a stall, then a hard restart. Your GP problem could mask the first start since the fuel in the IP is expelled unburnt. By the time combustion chamber temperature is high enough for the engine to fire, there's no fuel, and you have to crank until the lift pump refills the filter.

Drain-back is usually caused by a leak in the fuel return system. When the engine runs sometimes a leak is visible, sometimes not. When it shuts off, the leak allows air to enter the system, causing fuel to drain back to the tank. Search this forum for "clear line test" for help with locating the problem.

 

[mobiledj911]

Well I got them all out as you said with patience! It remains hard to start, only marginally better. only two tested above 2 ohms. I did notice some corrosion on the connectors, could that be it? Is there a meter test i can run? Thanks

 

[standbypowerguy]

Corrosion adds resistance, clean it up. You can check the voltage on each GP to ground while the relay is engaged, should be 9-10 volts with good batteries. Speaking of which,. you should have two known-good batteries of at least 850 CCA installed. Marginal batteries can cause hard starting issues. Check the voltage across each battery when the engine is cranking, it shouldn't drop below 9. If it does, recharge, then get them load tested individually on a carbon pile. Always replace batteries in pairs.

Dirty connections or a bad starter can also cause hard start problems. With good, fully-charged batteries, the engine should crank fast enough that you can't count the revolutions. If it turns slow, check all of the cable connections, including grounds, and clean or replace as needed. Try again with charged batteries, if it still cranks slow, pull the starter and have it tested by a starter-generator repair shop. Generally speaking, the auto parts stores don't test starters correctly.

I've found that waiting until the GP relay kicks off works quite well. Turn the key to ON, the WTS light will come on then go off. Tap the go pedal once to set the fast idle. You'll see the factory voltmeter hanging low, about 9 or 10. After a few more seconds you'll hear a soft click and the voltmeter will jump, that's when you crank. When I do this in the summer, mine starts within the first second or two. In winter I do the same, but hold the go pedal down per the the instructions on the sun visor. Takes a little longer in winter, but always starts the first try. If I have time to be kind to the batteries, I plug in the block heater for 2-3 hours before I start it, then it works like summer.

 

[RonKZ650]

Of course all glow plugs are wired in parallel so all will read the exact same voltage at the wiring regardless of whether the plug is good or bad or wiring connections corroded so taking voltage readings at more than one plug is worthless. Batterys are also in parallel so what volts are on one battery is on the other. I sold my 89 back in 96 to get the 97 powerstroke, but for sure even one bad plug makes an 89 hard to start. On the 97 I had 4 bad and it was hard to start about the same as 1 on the 89.