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30 October 2018
Category: Ecobion Labs News
Posted by: Ecobion Labs

We have use of a HUGE garage for continuing our restoration work on the GMC.

14 July 2017
Category: Lab Blog
Posted by: Ecobion Labs

A bit of tidying up with new Repairs and Weekends Projects Categories making it easier to find things.

21 June 2017
Category: Lab Blog
Posted by: Ecobion Labs

We've just received our new JGAURORA Prusa i3 3D printer!


GMC Safari Restoration - Part 2 - Getting it started

Issue Number 1, the engine won't start!

So, I've got the battery charged up, power is going to the ignition, the dashboard display lights come on, but normally, you also hear a click followed by a whirr.

I'm not getting either.

So, this leads me to believe that there's something not right with the fuel pump relay...

On investigation, I found the insides of the relay contacts area to be completely gunged up with some kind of dark brown tar substance, also on the connector block. I bought a new relay from the USA, and cleaned up the contacts.

GMC Restoration - New Fuel Pump Relay

The relay is the square block in the picture above. On my 1991 Safari, it's located on the top rear left-hand side of the engine compartment, looking under the bonnet toward the vehicle.

With a new relay and cleaned contacts, turned the key, got my click and a whirr, which means all seemed to be working, and it started. Problem solved? No.

After about a minute, the engine started to struggle and cut out. I could get it started again, but it cut out again, and the more I tried the worse it got. One problem fixed leads to a new problem to fix.

So, issue number 2, the engine still won't start!

The local garage seemed to think the problem was old petrol. So the first job was to dump about 30l of petrol out of the petrol tank. I tried siphoning it, but the tank contains an anti-siphon device. To be honest, when it started up it ran very well, but after 30 seconds to a minute, it would only then splutter. If petrol was to blame then surely, it would be spluttering from the start?

I took the air filter off to reveal the carburettor, and located the fuel line going into it. I attached a length of clear hose (with the help of some insulation tape to keep it in place) and started to pump it out. Loads of pumping later, I have a couple of hundred millilitres. There had to be a better way, and I had an idea.

GMC Restoration - Fuel Extraction

The whirring sound when the ignition is turned on is the fuel pump priming - it pumps out a small amount of fuel to build pressure ready to start. I turned on the ignition, and fuel squirted out! So I took advantage of this, turning the ignition on and off, filling up my petrol can squirt by squirt, until all of a sudden, the fuel pump stopped working.

As I suspected, the fuel pump is possibly overheating after it has been running for a short time. I left it alone for about an hour went back, and it worked again for a while, same thing, and again, and again.

So, looks like a new fuel pump, which means dropping out the fuel tank from underneath the car.

Issue number 3, Bolts holding the fuel tank are just spinning!

The fuel pump was replaced not long before the vehicle was last used, and I remember being told that they had trouble with the bolts.

My problem is that the bolts seemed to be spinning around. The captive nuts were no longer captive. Strangely there was an external nut on the bolt, which I think the garage used to lock the bolt in place.

GMC Restoration - Captive Bolt

My options are limited, and I have some difficulties with this:

- The tank probably weighs well over 100kg when full, so mounting needs to be strong.

- I have a problem with both outside bolts. I would prefer not to try the inside bolts because of access underneath, and a load of cables and pipes running along the other side of the tank as well as the exhaust.

- Access to the first bolt is relatively easy, thanks to the wheel arch, but the second bolt with the same problem is much more difficult to get to because of bodywork in the way.

With fuel tank drained as much as possible, and a jack placed underneath to take the weight, I cut off the bolt heads with a Dremel fitted with a cut off disc.

Turning the bolt into a stud

Moving the straps down, I was able to lower the tank a few inches, however, the hoses were catching and preventing the tank from being lowered more.

Issue 4: Disconnecting the hoses.

Access to the top of the tank was too restrictive, so disconnecting the hoses there turned out too difficult. I couldn’t get a screwdriver in to loosen the jubilee clips or grip the hoses adequately to slip them off. Between the fuel tank and the exhaust is a space that’s just large enough to get a hand and pair of adjustable pliers through.

Flexible hoses connected to solid lines

Loosening the pipes using the pliers helped a lot, some were quite seized and would never have come off by hand. They all pulled off ok, noting which ones went where.

The large hose that connected the fuel filler into the tank also had to be slipped off.

Fuel Filler Side Hose Removed

This was prised off one end with a screwdriver after the jubilee clip was loosened. This was fairly tricky; access was very limited, and the pipe had to be bent around anything in its path.

I was then able to drop the tank all the way down. Lowering it with the jack, while negotiating the straps out of the way.

Lowering the fuel tank using jacks for support

I needed to remove the tank completely to get to the sender unit (that contains the gauge), so slid the jack out, and then dragged the tank out from underneath. The empty tank wasn’t all that heavy, a lot lighter than I expected.

Fuel tank removed

Removing the sender unit

With the tank removed completely, it’s a lot easier to access the sender unit. This would have been impossible from underneath the car with the tank in place.

Easy access to sender unit with fuel tank removed 

Using a hammer and a screwdriver, I carefully tapped a retaining ring lose, and the sender unit simply lifted out revealing the pump and fuel gauge mechanism.

Sender Unit Retaining Ring

Various sources suggest a brass punch be used to prevent sparks, but to be honest, with the fuel removed, and a gaping hole in the side from the fuel filler hose, I don't really see the possibility of sparks while the sender is seated. Under other circumstances, I may have followed the advice.

Some videos on YouTube show people cutting access holes in the floor for access. With hindsight, I’m pleased I didn’t do this, the temptation was there, and I could possibly have messed up the correct location, as some YouTube videos did (and kept expanding the hole until it was large enough for access). It may be a bit of hard work dropping the tank, but I believe it’s worth it.

Replacing the pump

There were no instructions with the replacement pump. I looked up a few YouTube videos that showed that the new pump had to be spliced in. There are no internal connectors on the sender unit, so it was necessary to cut the wires, remove the pump and solder wires for the new pump. I added some heat-shrink sleeving over the solder joints. I’m not sure how well they will hold up to petrol, but I’m sure this is better than electrical tape, and the solder joints were staggered to minimise potential of contact. These wires are always covered in petrol, so it’s a little worrying. I added a couple of cable ties to space the wires apart a bit. I haven't posted a photo, as it's quite straightforward, and the YouTube videos out there are very detailed.

 The pump was refitted into the sender unit (having added the filter that came with it), and the sender unit was reinstalled into the tank. The retaining ring was taped back into position. I took advantage of having the tank available to sand down some of the surface rust and apply a touch of spray paint. Wasn’t necessary, but I felt better for doing it.

Re-installing the tank

With the tank lifted up back onto the jack, the straps were brought back around the tank as it was lifted. It didn’t quite go to plan. The tank got hung up a few times on the cable for the pump, as well as the handbrake cable that runs along the side. The fuel filler hose was constantly getting in the way and had to be persuaded. Finally, with the tank in place, it was a matter of bolting the straps back on.

As the straps had bent when the tank was removed, they had lost some girth and wouldn’t stretch to the bolts. To resolve this, I used a long screwdriver and jacked the ends of the straps to the bolts, effectively forcing them in position. I was only just able to get the nuts on, and without the supporting washers. I believe that in time, the straps will readjust giving a little more slack, and I can later fit the washers but for now, the straps are on there good and the tank is back in place. The hoses were refitted.

The moment of truth!

So, with the fuel line reconnected to the carburettor, some fuel added, the battery reconnected, put the key into the ignition, and got the click followed by the whirr. A good sign. Turned the key more and the engine turned over one revolution and fired up immediately. And, it didn’t cut out, it idled beautifully, and giving a few revs, there was no hesitation. An age had passed, days of problem solving with limited knowledge and basic tools and I had fixed the engine start problem. The GMC could now be moved so I could start to tackle all the other problems.

 Suffice to say, moving it was not without problems. I pulled the old exhaust tailpipe off, it was dragging along the floor, and a couple of the brakes were completely seized, but the 4.3l engine pushed right through that. Yes, brakes are the next big job, but at least I have a temporary dry garage to do much of the remaining work in - But a limited time available!

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